Fruit Trees for Burley, Rupert, Heyburn and Paul, Idaho

In the January 1962 cold snap the Minidoka Dam station hit −41°F, the coldest reading any NOAA station around here has on file, while the old Burley station, 17 miles down the Snake, bottomed out at −25°F. The Mini-Cassia looks dead flat from I-84, but on a clear, still night it isn't, and picking fruit trees for Burley, Rupert, Heyburn and Paul starts with knowing which part of the flat you're on.

This map covers the South Side from Burley east to Declo and south to Albion, and the North Side Tract from Heyburn and Paul through Rupert and Acequia to Minidoka and the west end of Lake Walcott. Type your address in the box on the map to get the number for your own place, and the list of what we sell that has come through it.

How to read this map

Every number on the map is a 30-year planning low, the same number our cold hardiness calculator gives, built from NOAA station records since the 1995-96 winter and adjusted for the lay of the land. It's a safe number to plan around, not the record. You also get the MFTC zone (that number in half zones), the typical winter (an average year's coldest night, the kind of number USDA's map is built on, which is why USDA zones read warmer) and a spring layer: how much warmer or colder a spot runs than downtown Burley on a still, clear night at bloom.

Burley, the reference town, plans for −19°F (MFTC zone 5a) with a typical winter of −2°F, and Rupert comes out the same. The middle of the growing ground plans for −21°F (zone 4b), and the spread is narrow: half the ground falls between −22°F and −20°F, nine tenths between −24°F and −18°F. The warm end is the southwest corner toward Oakley, the buttes (Burley Butte −16°F) and the two town centers. The cold end is the north end of the map, where Norland plans for −25°F, and the floor of Albion's valley, also around −25°F.

Why the map looks the way it does

Nearly all of this is Snake River Plain, irrigated and close to level. The river drops only from about 4,282 ft at Minidoka village to 4,134 ft at Milner Lake, Cassia County's lowest ground, and Rupert, Heyburn, Paul and Burley all sit at about 4,145 to 4,160 ft. On ground that flat the cold doesn't drain anywhere in a hurry; most of it is made right where it sits, as open ground radiates to a clear sky. Almost every named place on the floor sits 0 to 50 ft above its local low ground, which is why the spread is narrow and a few feet of height count for so much.

The warmest spots on the floor are the town centers. Burley and Rupert both plan for −19°F, while the floor within 3 miles runs a median of −20°F around Burley and −21°F around Rupert. Pavement and buildings hold heat on still nights, and the old records fit that. The old Burley station (1918 to 1966) ran a median 4°F warmer on the year's coldest night than the Burley airport station, a mile away and 40 ft lower. In six big outbreaks from 1933 to 1962, the Rupert 3 WSW station, 3 miles west-southwest of town, read 3°F to 7°F colder than the old Burley station in the same cold snap.

The cold end is the north side, away from the river and the towns. Minidoka village, at 4,276 ft, plans for −22°F and Norland, at 4,290 ft, −25°F, the coldest planning low of any named place here. Higher than Rupert and still colder: that fits broad, open ground that makes its own cold, with no town on it to hold heat. The old Minidoka 10 WNW station, at the same 4,290 ft, had only 12 years on file but averaged −14°F for its yearly low and was the coldest station in the December 1972 and February 1985 outbreaks (−29°F and −30°F).

Minidoka Dam is the other cold spot. Its station, at 4,164 ft at Lake Walcott's outlet, runs a median 5°F colder on the year's coldest night than the old Burley station. We haven't found a published explanation. It fits low ground by the river in open country, and the lake doesn't help: Lake Walcott freezes enough for ice fishing, and frozen water doesn't moderate its shore the way open water does. The map plans for −22°F there, the station's own 30-year number.

The South Side climbs gently south toward the mountains, and its southwest corner holds some of the mildest farm ground on the map: Kenyon, at 4,305 ft, plans for −19°F and Churchill, at 4,377 ft, −18°F. Oakley, just off the map at 4,559 ft, shows the same thing on the worst nights: −8°F in the February 1985 cold snap while Minidoka Dam read −29°F and the Burley airport −26°F. The University of Idaho's Cassia County office says Oakley tends to run slightly warmer than Burley and Malta colder, and that frost-free days on the farm ground vary with air drainage.

Get up off the plain and it warms more. Burley Butte, 370 ft above the floor southwest of town, plans for −16°F, the warmest planning low of any named place on the map. On a still spring night the gap grows: Burley Butte runs 9°F warmer than Burley at bloom, Antelope Hill (310 ft up, south of View) 11°F and Kimama Butte (570 ft above the north side) 14°F. That's the thermal belt, the slope band above the night's cold pool.

On the deepest arctic nights the pattern can flatten. In the December 1990 outbreak the Howell Canyon station, up at 7,980 ft, read −26°F, the same as Minidoka Dam on the floor. When arctic air pours in on a wind there's no inversion and height buys nothing. Spring is windy here too (the extension office calls wind common in most springs), and a windy freeze ignores the warm ground the spring layer shows.

Burley and Heyburn on the Snake

Burley sits mostly on the south bank in Cassia County, with a sliver north of the river, and Heyburn adjoins it across the Snake. Burley plans for −19°F (5a), typical −2°F. There's no bench ground within 3 miles, just floor: a median of −20°F, the warmest tenth of the growing ground at −19°F and the coldest at −21°F. So Burley's edge fits the built-up blocks around Overland Avenue, the courthouse and Centennial Park, not height. There's no frost-date station in town; the nearest is the Burley airport station, on the floor near town and colder than the old Burley station on winter nights (its dates are in the spring section).

Heyburn, first called Riverton, plans for −20°F (4b), typical −4°F, with its floor at −20°F, the warmest tenth −19°F and the coldest −22°F. On a still spring night it runs about 1°F colder than Burley. West of town the floor drops toward Milner Lake, and Hobson, on low bottom ground at 4,145 ft, plans for −22°F and runs 4°F colder than Burley at bloom.

Here the winter number clears nearly everything we sell. Contender and Veteran peaches (−30°F), Tomcot apricot (−30°F), Rainier sweet cherry (−30°F; dry country suits it, since it cracks where it rains at ripening), Stanley plum (−30°F) and Purvis Hardy English Walnut (−25°F) all have room. Bloom is the limit: give the apricots and peaches the highest, best-drained corner of the lot and let apples have the low end.

Rupert, Paul and the North Side Tract

Rupert, the Minidoka County seat, sits about 3 miles northwest of the Snake on the North Side Tract, the gravity-watered farm ground on alluvial soils between Minidoka, Rupert and Heyburn. Rupert plans for −19°F (5a), typical −2°F, but the country around it runs colder: the floor within 3 miles has a median of −21°F, the warmest tenth −20°F and the coldest −22°F. That's the biggest gap between a town and its floor of any town on the map, about 3°F, so a lot near Historic Rupert Square has an edge a place a mile out doesn't. Toward Heyburn, Amalga and Schow plan for −21°F and −22°F and run about 2°F colder than Burley in spring; Travers, on bottom ground at 4,145 ft, plans for −22°F and runs 4°F colder.

Paul, 6 miles west of Rupert, sits right on the floor at 4,145 ft, 0 ft above its local low ground. It plans for −22°F (4b), typical −5°F, with its floor at −21°F and the warmest and coldest tenths at −20°F and −22°F. The Paul 1ENE station agrees, with a 30-year number of −22°F and a median 4°F colder than the old Burley station over 25 years. Its spring frost dates run close to the Burley airport's, though, and it's the nearest frost-date station to Rupert, which has none.

West of Paul the floor gets frostier in spring. Budge runs 2°F colder than Burley on a still bloom night, and Hynes, on bottom ground at 4,174 ft, runs 7°F colder, the coldest spring reading of any named place on the map, while planning for −22°F in winter.

On the North Side the winter number still clears a long list: Honeycrisp (−45°F), Liberty (−35°F) and Northern Spy (−30°F) apples, Summercrisp (−45°F) and Flemish Beauty (−40°F) pears, Italian plum (−35°F) and Meteor tart cherry (−40°F). On bottoms like Hynes and Travers skip the pears (they bloom early) and give that ground to apples, honeyberries and Montana Black Currant.

Acequia, Jackson, Minidoka and Lake Walcott

East of Rupert the North Side runs up the river toward the dam. Acequia (ah-SEE-kwa, Spanish for a canal, where the Main A and B canals split off the main canal) sits on river-bottom ground at about 4,160 ft. It plans for −21°F (4b), typical −4°F, and runs 3°F colder than Burley in spring. Jackson, 4 miles east of Rupert with the Snake just northwest of it, is about the same. Minidoka village, the county's first permanent settlement (a railroad siding and watering stop in 1884), is higher at 4,276 ft and colder anyway: −22°F, typical −6°F, with the coldest tenth around it at −23°F. The dryland homesteads around Minidoka and Kimama had all failed by 1932, beaten by too little rain plus frost, wind, weeds and pests.

The Minidoka Dam station sits at a dam on the river, not in a town, and its frost dates are the latest of the three floor stations that have them (a median last 32°F of May 15, against May 2 at the Burley airport). Lake Walcott ices over, so don't count on it for winter shelter. Mule deer, pronghorn, moose, elk and cottontails all use the Minidoka National Wildlife Refuge above the dam, so fence young trees and guard the trunks.

Up here, at −22°F to −25°F, lean on the hardiest picks: Haralson (−45°F) and Wealthy (−50°F) apples, Kerr and Trailman applecrabs (if you only plant one tree, make it one of these), Ure pear (−45°F), Mount Royal plum (−45°F) and Evans Bali tart cherry (−45°F).

Declo, Springdale, Unity and View

Declo, first called Marshfield, sits 9 miles east of Burley just south of the Snake at about 4,218 ft, 50 ft above its local floor, with rising ground to the southeast where the hillside "D" stands. It plans for −20°F (4b), typical −4°F; the floor around it runs −21°F and the benches −20°F. In spring it reads about 1°F warmer than Burley, the best spring reading of any of the towns. Springdale, 5 miles east of Burley, plans for −21°F and reads even with Burley at bloom. Unity, between them on a 5 percent toe slope 50 ft above the floor, plans for −21°F in winter but runs 4°F warmer than Burley on a still spring night, because the cold slides off a slope like that instead of sitting on it. View, at 4,232 ft toward the Albion Mountains, plans for −21°F and runs 2°F colder than Burley at bloom.

Ground like Unity's and the rising side of Declo is where the early bloomers go on this side of the river: SnowCzar almond (−25°F), Harlayne (−30°F) and Westcot (−45°F) apricots, Siberian C peach (−35°F) and Lapins sweet cherry (−35°F). Lapins and Gold are the hardiest sweet cherries we've found.

Kenyon, Pella, Beetville and the southwest corner

Kenyon plans for −19°F (5a), typical −3°F, and Churchill −18°F (5a), but both run about 2°F to 3°F colder than Burley on a still spring night, so the winter gain doesn't carry into bloom. The rises do better: The Knolls, 130 ft above the floor on a 9 percent slope beside Churchill, plans for −17°F and runs 10°F warmer than Burley at bloom. Closer to town, Pella and Beetville sit about a mile apart at the same 4,232 ft and plan for −21°F and −20°F. In spring Pella, in a bottom 10 ft above the low ground, runs 4°F colder than Burley, while Beetville, 40 ft up on a 3 percent slope, reads even with it. That's a 4°F bloom-night swing across a mile of the same farm country, and it's the kind of thing to look for on your own place.

In Kenyon and Churchill the winter number clears nearly the whole list, even our −20°F trees like Santa Rosa plum, and the −25°F peaches like Redstar and Glohaven have room to spare. Let the spring reading decide where on the place each one goes.

Albion and Marsh Valley

Albion breaks the rule that higher is warmer here. It sits at about 4,725 ft in the old Marsh Valley at the foot of the Albion Mountains, about 570 ft above Burley, and plans for −23°F (4b), typical −8°F. The valley floor around it runs −25°F and the benches −23°F. That fits a mountain valley that collects cold air off the slopes above it and holds it. The old Albion station had only 13 years on file (1901 to 1952), but it averaged −12°F for its yearly low and read −27°F in the January 1949 cold snap, as cold as the Burley airport. Albion was the first Cassia County seat, and in spring the town reads only about 1°F colder than Burley.

The benches run about 2°F warmer than the floor. Trees rated −25°F clear the town and the benches but sit right at the line on the floor, so lean harder the lower you go: Centennial applecrab (−50°F; Ed Schultz saw zero winter injury on it after a winter that hit −47°F), Zestar!® apple (−40°F), Luscious pear (−40°F), Toka plum (−45°F), and Debbie's Gold apricot (−45°F) on the bench.

Spring frost and bloom in the Mini-Cassia

Most of what we sell clears the winter here, so for most yards the real question is bloom. Open blossoms of apples, pears, cherries, peaches, apricots and plums all start dying at about 28°F (Michigan State's fruit people). On a still, clear night that cold settles first in the bottoms around Paul (Hynes 7°F colder than Burley, Travers 4°F), at Hobson and Pella (4°F) and at Acequia and Jackson (3°F). The town centers read about even, and the toe slopes and rises are the safest ground at bloom, from Unity at 4°F warmer to Kimama Butte at 14°F.

The stations' 1991 to 2020 medians:

• Burley airport (4,143 ft, on the floor near town): last 32°F May 2, last 28°F April 20, first fall 32°F October 5, 148 frost-free days; one year in ten the last 32°F comes May 23 or later.
• Paul 1ENE (4,150 ft, on the floor east of Paul, 19 years): last 32°F May 4, last 28°F April 29, first fall 32°F October 4, 152 frost-free days.
• Minidoka Dam (4,164 ft, at the dam): last 32°F May 15, last 28°F May 2, first fall 32°F September 30, 134 frost-free days; a late year runs to June 10.
• Oakley (4,559 ft, a town just off the southwest edge): last 32°F May 14, first fall 32°F October 3, 137 frost-free days.

May 2002 is the local reminder of what spring can do. Burley fell to 28°F on the second straight night below freezing, beet growers had already replanted more than 7,000 acres, and Aberdeen and American Falls upriver took the worst of the cold and wind (the Pocatello and Blackfoot map covers that stretch). In April 2024 a frost took the whole cherry crop at Kelley Canyon Orchard near Filer, in the Twin Falls and Magic Valley country, while the plums came through.

Site comes first; the FAO's frost manual calls it the single most important method of frost protection, and on a floor this flat that means height off the low ground. Minnesota's fruit people say even 20 ft of drop inside an orchard can make a difference, and the University of Idaho's apple bulletin for cold, short-season country says to look for good cold-air drainage on a 2 to 4 percent slope. Put apricots, peaches, almonds and sweet cherries highest, plums and pears next, and apples, haskap and bush fruit at the low end. Haskap flowers take 19°F wide open, and an apple tree needs only about 15 percent of its blossoms to set a crop. A canal bank, a road fill or a thick hedge on the downhill side can back cold air up into the trees above it. On a frost night, mow short, don't till, water a day or two ahead and cover small trees; frost cloth of 0.5, 0.9 and 1.5 oz per square yard gives about 4°F, 6°F and 8°F (Alabama Extension's numbers). Height and drainage only help on still, clear nights, not in a windy freeze.

What the weather records say

NOAA station records here go back to the 1890s at Oakley, and the coldest of them is the −41°F at Minidoka Dam on January 22, 1962. In the same cold snap Rupert 3 WSW read −32°F, the Burley airport −30°F, Paul 1ENE −28°F, the old Burley station −25°F and Oakley −23°F. Other station records: the old Burley station −35°F on January 19, 1922; Rupert 3 WSW −33°F on January 21, 1937; Paul 1ENE −31°F on January 25, 1949; the Burley airport −30°F in 1949 and again in 1962. Average yearly lows run from −7°F at Oakley to −14°F at Malta 4 ESE, just off the southeast edge.

Utah State University worked out zones from 1990 to 2019 station data: an average yearly low of −4°F at the Burley airport, Paul and Oakley (zone 6b) and about −8°F at Minidoka Dam (6a). That's the same kind of average-winter number USDA's map is built on; ours plans for the bad night, so Burley comes out MFTC 5a and most of the farm ground 4b. Burley has seen −14°F in November, and a night like that hits trees before they've hardened off.

What you can grow here

Nearly every plant we sell is rated −25°F or colder, and nearly all the ground here plans for −25°F or warmer. The bands below are about what clears with room; the spring reading decides where it goes.

Town centers, the southwest corner and the rises, −20°F or warmer

Burley, Rupert, Heyburn, Declo, Kenyon, Churchill and the buttes. Peaches: Blushingstar (−30°F) and Contender. Apricots: Harlayne and Goldrich (−30°F). Sweet cherries: Rainier and Stella (−25°F). Plums: Shiro (−30°F) and Stanley. Pears: D'Anjou (−30°F) and Seckel (−35°F). Apples: Cox Orange Pippin (−35°F). Also Hardired nectarine (−25°F) and Purvis Hardy English Walnut. Santa Rosa plum (−20°F) clears the −19°F town centers; in Heyburn and Declo it's worth a try on a south wall.

The irrigated floor, −21°F to −23°F

Paul, Acequia, Jackson, Springdale, View, Minidoka and most of the farm ground. Apples: Honeycrisp, Liberty, Sweet Sixteen (−40°F) and Northern Spy. Pears: Summercrisp and Bartlett (−35°F). Plums: Toka and Superior (−35°F); Toka is a good pollenizer for Superior, and our pollination maps show the other pairings. Cherries: Meteor and Black Gold (−35°F). On your highest ground, Siberian C, Contender and Westcot. Grapes: Marquette (−35°F) and Valiant (−50°F).

The coldest ground, −24°F to −25°F

The north end around Norland and the floor of Albion's valley. Haralson, Wealthy, Centennial, Kerr and Trailman; Ure and Bolshaya (−50°F) pears; Mount Royal and Brookgold (−50°F) plums; Evans Bali tart cherry; Westcot and Debbie's Gold apricots on any rise you've got. The −25°F trees sit right at the line here, so save them for the warm side of the place.

Berries, anywhere on the map

Honeyberries, Montana Black Currant, Red Lake currant (−40°F), Invicta gooseberry (−40°F), Boyne raspberry (−50°F) and aronia (−50°F) have room anywhere here, and they're the right crop for the frosty bottoms.

Roots, water, soil and wind

The extension office notes there's little snow on the valley floor, and that matters for roots. Roots are the weak link, and snow is what protects them: at Ed Schultz's farm in Gallatin Gateway, Montana, Bud 118 apple rootstock has seen near −50°F with no rootstock damage, under snow. On bare ground, mulch the root zone and hold what snow you get. We taper water from mid-August in zone 4 and colder so trees harden off, but dry soil means more root death in a hard winter, so don't send the roots into winter bone dry. Drip is the only irrigation we advise for fruit trees in dry country.

The Minidoka soil series, common on the terraces and basalt plains of south-central Idaho, is calcareous right to the surface, slightly to strongly alkaline, with a hardpan 20 to 40 inches down and basalt below that. Do the drainage test where the tree's going (dig 2 ft, fill it, let it drain, fill it again; under 10 hours is well drained). For wind, Montana State calls for a windbreak at least the height of the fruit trees, and the University of Idaho says to keep it 20 ft or more from the fruit and limb it up 4 to 5 ft so cold air can drain under it.

Fruit history here

Fruit is on the Minidoka Project's crop list, next to potatoes, alfalfa and sugar beets. Minidoka Dam went in from 1904 to 1906, Reclamation's first project in Idaho; north-side water came in 1906 and 1907 and ran by gravity, while the south bank around Burley had to be pumped. In 1959 the University of Idaho's fruit bulletin covered Burley, Rupert and Oakley and told growers to keep fruit on ground with good air drainage. We haven't found a historic orchard district, a locally bred variety or a commercial orchard inside the map.

Questions people ask

What growing zone is Burley, Idaho?

Our map plans downtown Burley for −19°F, MFTC zone 5a, and most of the farm ground around it for −20°F to −22°F, zone 4b. Utah State University's zone calculation from 1990 to 2019 station data gives the Burley airport an average yearly low of −4°F, zone 6b. That one's based on an average winter; ours is the bad night we plan for.

When is the last frost in Burley and Rupert?

At the Burley airport station the 1991 to 2020 median last 32°F frost is May 2, and one year in ten it comes May 23 or later. Rupert has no frost-date station; the Paul 1ENE station, a few miles west, has a median of May 4. The Minidoka Dam station, at the dam east of Rupert, runs later, to May 15.

Can you grow peaches in Burley?

Yes. Downtown Burley plans for −19°F (MFTC 5a), and Contender, Blushingstar and Veteran (−30°F) and Siberian C (−35°F) all clear it with room. Bloom is the risk, so plant peaches on the highest, best-drained ground you have and keep them out of the bottoms.

Can you grow apricots in the Mini-Cassia?

The trees will live: every apricot we sell is rated −30°F or colder, and nearly all the farm ground here plans for −17°F to −25°F. The crop is the gamble, because apricots bloom first. Put them on a toe slope like Unity's (4°F warmer than Burley on a still bloom night) or a bench, and keep them off the bottoms.

Is Oakley warmer than Burley?

On the worst winter nights, yes. In the February 1985 cold snap the Oakley station read −8°F while the Burley airport read −26°F, and the University of Idaho's Cassia County office says Oakley tends to run slightly warmer. Spring goes the other way: the Oakley station's 1991 to 2020 median last 32°F frost is May 14, against May 2 at the Burley airport.

Does Lake Walcott freeze?

Yes, enough for ice fishing. A frozen lake doesn't warm its shore, and the Minidoka Dam station at its outlet holds the coldest reading of any station here, −41°F on January 22, 1962.

Warmer spots, colder spots

Here's the number to plan for at named places on the map, warmest first. Each one is the 1-in-30-year low for that spot: the cold hardiness calculator's number from the same weather stations, sharpened by our microclimate model for the ground right there. Zone is our MFTC zone, set by that one bad night, not by an average.

The weather stations behind it

These are the long-record stations in and around this map, with each one's own numbers since the winter of 1995-96. The last column is this map's 30-year number right at the station, which won't match the station exactly: it's a blend of the stations around it, the way the calculator works everywhere.

Source: NOAA records through ACIS, winters 1995-96 through 2025-26. What the "carried forward," "gaps filled" and AWOS rows mean is explained in how our microclimate maps work.