Frost Dates for East Helena, MT

Based on data from Helena Rgnl AP weather station, 3 miles away

Elevation: 3888 ft

Frost Dates

Last Spring Frost (50%) A 50% chance that the last spring frost has already passed by this date. Most gardeners use this as their primary planting guide. May 9
First Fall Frost (50%) A 50% chance that the first fall frost has occurred by this date. Plan to harvest or protect tender plants before this date. September 30

30% Probability

Only 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 15
First Fall Frost September 25

Hard Freeze (28°F)

Last Spring Hard Freeze April 29
First Fall Hard Freeze October 7
46.59°N, 111.92°W © OpenStreetMap

Growing Season

144 Days May 9 to September 30

USDA Hardiness Zone

Hardiness 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 5a

Avg. annual minimum: −20 to −15°F

Learn more

Köppen Climate

The Köppen climate classification system categorizes climates based on temperature and precipitation patterns.
BSk Cold Semi-Arid (Steppe)

Cool to cold with low rainfall and wide temperature swings. Common in the western Great Plains and central Asia. Short growing seasons benefit from season extension techniques.

Köppen climate map

Temperature

Avg High Avg Temp Avg Low Light Frost (32°F) Hard Frost (28°F)
Temperature table
Average monthly temperatures (°F)
Month Avg High Avg Temp Avg Low
January32°23°14°
February37°27°17°
March48°36°25°
April57°45°32°
May66°54°42°
June75°62°49°
July86°71°55°
August85°69°53°
September73°59°45°
October58°46°34°
November43°33°23°
December33°23°14°

Precipitation

Precipitation table
Average monthly precipitation (inches)
MonthPrecipitation
January1.1
February0.8
March1.2
April1.8
May2.6
June2.9
July2.6
August2.8
September2.3
October1.6
November1.2
December1.1

Sunrise / Sunset

Daylight Mountain Time (MT) Longest: 15h 38m · Shortest: 8h 22m
Sunrise and sunset table
Sunrise, sunset, and daylight on the 15th of each month (Mountain Time (MT))
Month Sunrise Sunset Daylight
January8:14 AM4:60 PM8h 45m
February7:40 AM5:45 PM10h 04m
March7:49 AM7:26 PM11h 36m
April6:48 AM8:08 PM13h 21m
May5:60 AM8:48 PM14h 49m
June5:40 AM9:17 PM15h 37m
July5:55 AM9:12 PM15h 17m
August6:32 AM8:32 PM14h 00m
September7:13 AM7:32 PM12h 19m
October7:54 AM6:32 PM10h 38m
November7:39 AM4:47 PM9h 08m
December8:12 AM4:35 PM8h 23m

Nearby Stations

Austin 1 W, MT June 4 - September 14 Tizer Gardens, MT June 18 - September 5 Elliston, MTJune 9 - September 8 Holter Dam, MT May 19 - September 24 Boulder, MTJune 7 - September 8 Adel, MTJune 4 - September 12

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