Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 59824 — Charlo, MT

ZIP code 59824 (Charlo, Lake County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 12 and the first fall frost October 2.

Where ZIP 59824 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostMay 12
First frostOct 2
2012 zone5b

Was 5b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Charlo, MT…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Charlo, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 12median — 50% chance of a later frost
Safe for tender plantsJune 1only 10% chance of frost after
First fall frostOctober 2median — 10% chance by Sep 19
Growing season142 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 30 and returns around October 12.

From the NOAA station Saint Ignatius, MT — 9 miles away, elevation 2,917 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 59824

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 31 – Apr 14
SpinachSow outdoors · Mar 31 – Apr 21
Broccoli, cabbageStart indoors · Mar 3 – Mar 17
Broccoli, cabbageTransplant · Apr 21 – May 5
Onion setsPlant outdoors · Apr 14 – Apr 28
PotatoesPlant outdoors · Apr 21 – May 5
LettuceSow outdoors · Apr 14 – Apr 28
Carrots, beetsSow outdoors · Apr 21 – May 5
TomatoesStart indoors · Mar 17 – Mar 31
TomatoesTransplant · May 19 – Jun 2
Peppers, eggplantStart indoors · Mar 3 – Mar 17
Peppers, eggplantTransplant · May 26 – Jun 9
BeansSow outdoors · May 19 – Jun 2
Sweet cornSow outdoors · May 19 – Jun 2
Cucumbers, squashSow outdoors · May 19 – Jun 2
Fall lettuce, spinachSow outdoors · Aug 7 – Aug 21
GarlicPlant cloves · Sep 18 – Oct 23
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 12) and first fall frost (Oct 2) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 59824 came on Mar 29 — 11 days earlier than the 1991–2020 average (Apr 9).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Soil in Charlo, MT

The soil mapped at the center of ZIP 59824 is Post — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH8.5alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classFarmland of local importanceUSDA classification

Map unit: Post silt loam, 0 to 2 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 59824; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Charlo, MT

Summer high86 °Faverage high, July
Winter low22 °Faverage low, February
Hot days20days a year at 90 °F or more
Freezing nights152nights a year at 32 °F or less
Growing degree days2,070base 50 °F — the season’s usable heat
Longest day15 h 57 mindaylight on June 21
Shortest day8 h 27 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation16.7 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 37 °F, low 23 °F 37°23° JanFebruary: average high 40 °F, low 22 °F 40°22° FebMarch: average high 51 °F, low 28 °F 51°28° MarApril: average high 59 °F, low 34 °F 59°34° AprMay: average high 69 °F, low 41 °F 69°41° MayJune: average high 75 °F, low 47 °F 75°47° JunJuly: average high 86 °F, low 52 °F 86°52° JulAugust: average high 86 °F, low 51 °F 86°51° AugSeptember: average high 75 °F, low 44 °F 75°44° SepOctober: average high 59 °F, low 35 °F 59°35° OctNovember: average high 45 °F, low 28 °F 45°28° NovDecember: average high 37 °F, low 23 °F 37°23° Dec

Precipitation by month inches

0″1″2″3″January: 0.95 in precipitation 0.9 JanFebruary: 1.15 in precipitation 1.1 FebMarch: 0.94 in precipitation 0.9 MarApril: 1.75 in precipitation 1.8 AprMay: 2.30 in precipitation 2.3 MayJune: 2.63 in precipitation 2.6 JunJuly: 0.97 in precipitation 1.0 JulAugust: 1.17 in precipitation 1.2 AugSeptember: 1.51 in precipitation 1.5 SepOctober: 1.28 in precipitation 1.3 OctNovember: 1.13 in precipitation 1.1 NovDecember: 0.94 in precipitation 0.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Saint Ignatius, MT (9 mi away); precipitation: Saint Ignatius, MT (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

2 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

598636a
Ravalli, MT · 8 mi
598646a
Ronan, MT · 9 mi
598656a
Saint Ignatius, MT · 11 mi
598316a
Dixon, MT · 13 mi
598556a
Pablo, MT · 14 mi
598215b
Arlee, MT · 17 mi
598606a
Polson, MT · 21 mi
598465b
Huson, MT · 23 mi

Montana planting zones →

Questions about 59824

What planting zone is ZIP code 59824?

ZIP code 59824 (Charlo, MT) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Charlo, MT?

The median last spring frost (32 °F) near 59824 is May 12; after June 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Saint Ignatius station.

When is the first frost in Charlo, MT?

The median first fall frost near 59824 is October 2, giving a median frost-free growing season of 142 days.

When should I plant tomatoes in 59824?

Start tomato seeds indoors around Mar 17 – Mar 31 and set transplants outside around May 19 – Jun 2, one to three weeks after the median last frost.

How much rain and snow does 59824 get?

About 16.7 inches of precipitation a year (NOAA 1991–2020 normals, Saint Ignatius station).

How hot do summers get in Charlo, MT?

The average high peaks at 86 °F in July, with about 20 days a year at 90 °F or more.

What kind of soil does 59824 have?

The USDA soil survey maps Post at the center of ZIP 59824: silt loam, well drained, pH about 8.5 (alkaline).

Did spring come early in Charlo, MT in 2026?

Spring leaf-out near 59824 came on Mar 29 in 2026, 11 days earlier than the 1991–2020 average (Apr 9), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Charlo, MT?

Long-day onions: the longest day near 59824 is 15 h 57 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59824 change?

Yes. The 2012 USDA map put 59824 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.