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🍂 First Frost Dates for Circle, Montana 59215

The first 36°F frost date is 30% likely to be on Sep 5. (See detailed probabilities below.)

The first 32°F light freeze date is 30% likely to be on Sep 15. (See detailed probabilities below.)

(See also 🌷 Last Spring Frost Dates.)

First frost date probabilities for Circle, MT are based on historical climate data.

Always check your local forecast for the most up-to-date frost warnings.

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What is a First Frost Date?

The first fall frost signals the end of your local growing season. This date serves as an important deadline for gardeners and farmers. You'll need to complete harvesting before this point. Annuals and other tender plants will die back when frost hits, and perennial plants will enter their dormant phase for winter. Meanwhile, it's time to enjoy a cup of hot cocoa and a cozy sweater—and start planning your spring garden!

How to use the First Frost Date?

Watch your local weather forecasts in early fall to predict the first frost date. Harvest tender crops and protect vulnerable plants before frost arrives. For late-summer plantings, count backward from your area's average first frost date. This ensures your crops have enough time to mature. Keep track of when frost actually occurs in your garden each year. This helps you identify protected spots where the growing season might last longer.

First Frost Date Probabilities

Probability of frost (36°F) on or before...
10% chanceAug 28
20% chanceSep 2
30% chanceSep 5
40% chanceSep 8
50% chanceSep 10
60% chanceSep 13
70% chanceSep 16
80% chanceSep 19
90% chanceSep 23
Probability of light freeze (32°F) on or before...
10% chanceSep 6
20% chanceSep 11
30% chanceSep 15
40% chanceSep 18
50% chanceSep 20
60% chanceSep 22
70% chanceSep 25
80% chanceSep 28
90% chanceOct 2
Probability of moderate freeze (28°F) on or before...
10% chanceSep 15
20% chanceSep 20
30% chanceSep 23
40% chanceSep 26
50% chanceSep 29
60% chanceOct 1
70% chanceOct 4
80% chanceOct 7
90% chanceOct 12
Probability of moderate hard freeze (24°F) on or before...
10% chanceSep 22
20% chanceSep 27
30% chanceOct 1
40% chanceOct 4
50% chanceOct 8
60% chanceOct 12
70% chanceOct 15
80% chanceOct 19
90% chanceOct 24
Probability of hard freeze (20°F) on or before...
10% chanceSep 29
20% chanceOct 5
30% chanceOct 11
40% chanceOct 15
50% chanceOct 18
60% chanceOct 21
70% chanceOct 25
80% chanceOct 28
90% chanceNov 1
Probability of severe hard freeze (16°F) on or before...
10% chanceOct 7
20% chanceOct 15
30% chanceOct 19
40% chanceOct 22
50% chanceOct 25
60% chanceOct 29
70% chanceNov 1
80% chanceNov 5
90% chanceNov 11

Agricultural climatic data from weather station: CIRCLE (USC00241758)

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