Afton climate

Afton Frost Dates and Growing Season

NOAA 1991-2020 normals for Deposit, 20.2 km from Afton, elevation 1000 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Deposit. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around May 12 and the first fall freeze around October 9, a growing season of about 152 days.

Median at 36°F
last May 23, first October 1
Median at 32°F
last May 12, first October 9
Median at 28°F
last April 29, first October 24

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FJun 4May 31May 28May 25May 23May 20May 17May 13May 6
32°FMay 27May 22May 19May 15May 12May 9May 5Apr 30Apr 26
28°FMay 15May 10May 6May 2Apr 29Apr 26Apr 22Apr 18Apr 11
24°FMay 2Apr 27Apr 21Apr 18Apr 14Apr 10Apr 7Apr 3Mar 31
20°FApr 16Apr 10Apr 7Apr 4Apr 2Mar 31Mar 28Mar 25Mar 20
16°FApr 5Apr 2Mar 30Mar 27Mar 24Mar 22Mar 18Mar 15Mar 9

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 17Sep 23Sep 25Sep 28Oct 1Oct 2Oct 4Oct 7Oct 12
32°FSep 26Oct 1Oct 3Oct 6Oct 9Oct 11Oct 15Oct 19Oct 25
28°FOct 6Oct 11Oct 16Oct 20Oct 24Oct 27Oct 31Nov 3Nov 7
24°FOct 20Oct 27Oct 31Nov 2Nov 4Nov 8Nov 11Nov 15Nov 20
20°FNov 2Nov 7Nov 11Nov 14Nov 17Nov 20Nov 24Nov 28Dec 2
16°FNov 13Nov 19Nov 23Nov 26Nov 29Dec 1Dec 4Dec 8Dec 14

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F151144139134130127123118111
32°F173166161157152147142137130
28°F200192187182178174169163156
24°F226219213209205201195189181
20°F250242237232228225220215209
16°F272264259254249245241236230

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
6,594
Cooling degree days, base 65°F
510
Growing degree days, base 40°F
4,631
Growing degree days, base 45°F
3,527
Growing degree days, base 50°F
2,565
Growing degree days, base 55°F
1,736
Growing degree days, base 60°F
1,042

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,26201
February1,08200
March935010
April546369
May24628265
June5998490
July11181635
August21151595
September13246368
October4394116
November768014
December1,09401

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 20.2 km from Afton. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00302060 (Deposit). Public domain.