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🍂 First Frost Dates for Ontario, Oregon 97914

The first 36°F frost date is 30% likely to be on Sep 17. (See detailed probabilities below.)

The first 32°F light freeze date is 30% likely to be on Sep 27. (See detailed probabilities below.)

(See also 🌷 Last Spring Frost Dates.)

First frost date probabilities for Ontario, OR 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% chanceSep 9
20% chanceSep 14
30% chanceSep 17
40% chanceSep 19
50% chanceSep 22
60% chanceSep 24
70% chanceSep 27
80% chanceSep 30
90% chanceOct 4
Probability of light freeze (32°F) on or before...
10% chanceSep 19
20% chanceSep 23
30% chanceSep 27
40% chanceSep 30
50% chanceOct 2
60% chanceOct 4
70% chanceOct 7
80% chanceOct 10
90% chanceOct 15
Probability of moderate freeze (28°F) on or before...
10% chanceSep 29
20% chanceOct 3
30% chanceOct 6
40% chanceOct 9
50% chanceOct 12
60% chanceOct 15
70% chanceOct 18
80% chanceOct 21
90% chanceOct 26
Probability of moderate hard freeze (24°F) on or before...
10% chanceOct 9
20% chanceOct 15
30% chanceOct 19
40% chanceOct 22
50% chanceOct 25
60% chanceOct 28
70% chanceOct 31
80% chanceNov 3
90% chanceNov 10
Probability of hard freeze (20°F) on or before...
10% chanceOct 22
20% chanceOct 28
30% chanceNov 1
40% chanceNov 3
50% chanceNov 7
60% chanceNov 11
70% chanceNov 17
80% chanceNov 23
90% chanceNov 30
Probability of severe hard freeze (16°F) on or before...
10% chanceNov 1
20% chanceNov 7
30% chanceNov 13
40% chanceNov 19
50% chanceNov 24
60% chanceNov 29
70% chanceDec 3
80% chanceDec 9
90% chanceDec 18

Agricultural climatic data from weather station: ONTARIO MUNI AP (USW00024162)

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