🌷 Your Ultimate Garden Calendar!

🍂 First Frost Dates for Thompson Falls, Montana 59873

The first 36°F frost date is 30% likely to be on Sep 13. (See detailed probabilities below.)

The first 32°F light freeze date is 30% likely to be on Sep 26. (See detailed probabilities below.)

(See also 🌷 Last Spring Frost Dates.)

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

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

Book Recommendations (ads!)

📚 Growing Under Cover: Techniques for a More Productive, Weather-Resistant, Pest-Free Vegetable Garden

📚 Greenhouse Gardening for Beginners: Step By Step Guide To Build A Year-Round Greenhouse And Grow Herbs, Organic Fruits And Vegetables, Plants, Flowers Plans & Ideas for Extending the Growing Season

📚 How to Garden Indoors & Grow Your Own Food Year Round: Ultimate Guide to Vertical, Container, and Hydroponic Gardening (Creative Homeowner) Vegetables, Herbs, DIY Projects, Composting, Lights, & More

📚 The Year-Round Vegetable Gardener: How to Grow Your Own Food 365 Days a Year, No Matter Where You Live

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% chanceSep 5
20% chanceSep 10
30% chanceSep 13
40% chanceSep 16
50% chanceSep 19
60% chanceSep 22
70% chanceSep 25
80% chanceSep 28
90% chanceOct 2
Probability of light freeze (32°F) on or before...
10% chanceSep 17
20% chanceSep 22
30% chanceSep 26
40% chanceSep 29
50% chanceOct 1
60% chanceOct 3
70% chanceOct 6
80% chanceOct 10
90% chanceOct 16
Probability of moderate freeze (28°F) on or before...
10% chanceSep 29
20% chanceOct 3
30% chanceOct 6
40% chanceOct 10
50% chanceOct 14
60% chanceOct 18
70% chanceOct 22
80% chanceOct 27
90% chanceNov 1
Probability of moderate hard freeze (24°F) on or before...
10% chanceOct 8
20% chanceOct 18
30% chanceOct 23
40% chanceOct 28
50% chanceNov 1
60% chanceNov 4
70% chanceNov 10
80% chanceNov 15
90% chanceNov 23
Probability of hard freeze (20°F) on or before...
10% chanceOct 21
20% chanceOct 31
30% chanceNov 5
40% chanceNov 11
50% chanceNov 17
60% chanceNov 23
70% chanceNov 28
80% chanceDec 3
90% chanceDec 10
Probability of severe hard freeze (16°F) on or before...
10% chanceNov 1
20% chanceNov 12
30% chanceNov 20
40% chanceNov 27
50% chanceDec 1
60% chanceDec 6
70% chanceDec 11
80% chanceDec 17
90% chanceDec 27

Agricultural climatic data from weather station: THOMPSON FALLS PH (USC00248211)

Back to Weather Calendar