Alma climate

Alma Frost Dates and Growing Season

NOAA 1991-2020 normals for Alma Dam 4, 0.8 km from Alma, elevation 670 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Alma Dam 4. 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 April 28 and the first fall freeze around October 14, a growing season of about 168 days.

Median at 36°F
last May 7, first October 3
Median at 32°F
last April 28, first October 14
Median at 28°F
last April 17, first October 26

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°FMay 23May 17May 13May 10May 7May 4May 2Apr 29Apr 24
32°FMay 9May 5May 2Apr 30Apr 28Apr 24Apr 22Apr 18Apr 13
28°FApr 30Apr 26Apr 23Apr 20Apr 17Apr 14Apr 10Apr 7Apr 3
24°FApr 22Apr 18Apr 13Apr 9Apr 6Apr 4Apr 1Mar 30Mar 24
20°FApr 13Apr 7Apr 4Apr 1Mar 31Mar 28Mar 24Mar 20Mar 14
16°FApr 5Apr 1Mar 29Mar 26Mar 22Mar 19Mar 15Mar 12Mar 7

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 21Sep 25Sep 28Oct 1Oct 3Oct 6Oct 9Oct 12Oct 17
32°FSep 29Oct 3Oct 7Oct 11Oct 14Oct 18Oct 21Oct 24Oct 29
28°FOct 11Oct 16Oct 20Oct 23Oct 26Oct 29Oct 31Nov 3Nov 8
24°FOct 23Oct 27Oct 31Nov 1Nov 4Nov 6Nov 9Nov 12Nov 18
20°FNov 1Nov 4Nov 7Nov 10Nov 12Nov 15Nov 19Nov 22Nov 27
16°FNov 7Nov 11Nov 14Nov 17Nov 20Nov 23Nov 26Nov 30Dec 4

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°F167160155152148144140134128
32°F189182177172168164160156150
28°F209203198195190187182177170
24°F228222217213210206202197191
20°F247240235231226223219214209
16°F263256250246242238234228222

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
7,551
Cooling degree days, base 65°F
601
Growing degree days, base 40°F
4,604
Growing degree days, base 45°F
3,567
Growing degree days, base 50°F
2,641
Growing degree days, base 55°F
1,832
Growing degree days, base 60°F
1,147

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,51900
February1,25200
March1,005010
April573266
May24730270
June46126530
July9215671
August20162608
September14761373
October4986104
November908010
December1,32800

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 0.8 km from Alma. 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 USC00470124 (Alma Dam 4). Public domain.