Frost Dates for Bonner-West Riverside, MT

Based on data from Missoula 2 Ne weather station, 4 miles away

Frost Dates

Last Spring Frost (50%) iA 50% chance that the last spring frost has already passed by this date. Most gardeners use this as their primary planting guide. May 10
First Fall Frost (50%) iA 50% chance that the first fall frost has occurred by this date. Plan to harvest or protect tender plants before this date. October 1
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

30% Probability iOnly a 30% chance of frost remaining by this date. Use these dates for a safer planting window, especially for tender plants sensitive to cold.

Last Spring Frost May 17
First Fall Frost September 26

Hard Freeze (28°F)

Last Spring Hard Freeze April 28
First Fall Hard Freeze October 12
46.88°N, -113.89°W © OpenStreetMap

Growing Season

144 Days May 10 to October 1

USDA Hardiness Zone iHardiness zones indicate which perennial plants can survive winter in your area. For annual vegetables, frost dates and growing season length matter more than hardiness zone.

Zone 6a

Avg. annual minimum: −10 to −5°F (−23 to −21°C)

Learn more

Köppen Climate iThe Köppen climate classification system categorizes climates based on temperature and precipitation patterns.

Dfb Warm-Summer Continental

Warm summers and cold, snowy winters. A shorter growing season than hot-summer continental. Hardy vegetables, root crops, and cool-season greens do well. Season extension is valuable.

Köppen climate map

Temperature

10° 30° 50° 70° 90°
27°
High: 34°F
Avg: 27°F
Low: 20°F
Jan
30°
High: 39°F
Avg: 30°F
Low: 22°F
Feb
38°
High: 49°F
Avg: 38°F
Low: 27°F
Mar
45°
High: 57°F
Avg: 45°F
Low: 33°F
Apr
54°
High: 67°F
Avg: 54°F
Low: 41°F
May
60°
High: 73°F
Avg: 60°F
Low: 47°F
Jun
69°
High: 85°F
Avg: 69°F
Low: 52°F
Jul
68°
High: 84°F
Avg: 68°F
Low: 51°F
Aug
58°
High: 73°F
Avg: 58°F
Low: 44°F
Sep
45°
High: 57°F
Avg: 45°F
Low: 34°F
Oct
34°
High: 41°F
Avg: 34°F
Low: 26°F
Nov
26°
High: 33°F
Avg: 26°F
Low: 20°F
Dec
32°F
28°F
Avg High Avg Temp Avg Low Light Frost (32°F) Hard Frost (28°F)

Precipitation

0" 1" 2" 3" 3.1"
1.8"
1.82"
Jan
1.4"
1.40"
Feb
1.7"
1.71"
Mar
2.1"
2.10"
Apr
3.1"
3.06"
May
3.0"
3.01"
Jun
2.7"
2.70"
Jul
2.6"
2.60"
Aug
2.5"
2.48"
Sep
2.3"
2.29"
Oct
1.8"
1.80"
Nov
1.9"
1.86"
Dec

Sunrise / Sunset

4a7a10a1p4p7p10pNoonJanFebMarAprMayJunJulAugSepOctNovDec8.5h10h11.5h13.5h15h15.5h15.5h14h12.5h10.5h9h8.5h
Jan: 7:38 AM – 4:22 PM · 8h 43m
Feb: 6:58 AM – 5:02 PM · 10h 03m
Mar: 6:12 AM – 5:48 PM · 11h 36m
Apr: 5:19 AM – 6:41 PM · 13h 22m
May: 4:35 AM – 7:25 PM · 14h 51m
Jun: 4:10 AM – 7:50 PM · 15h 39m
Jul: 4:20 AM – 7:40 PM · 15h 19m
Aug: 4:59 AM – 7:01 PM · 14h 02m
Sep: 5:51 AM – 6:09 PM · 12h 19m
Oct: 6:42 AM – 5:18 PM · 10h 37m
Nov: 7:27 AM – 4:33 PM · 9h 06m
Dec: 7:50 AM – 4:10 PM · 8h 20m
Daylight Longest: 15h 41m · Shortest: 8h 19m

Nearby Stations

Missoula Intl AP, MT May 16 - September 26 Missoula 6 Nw Wfo, MT May 6 - October 4 Potomac, MT Alberton, MTMay 18 - September 25 Stevensville, MT May 22 - September 19 Saint Ignatius, MT May 12 - October 2

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