Alva climate

Alva Frost Dates and Growing Season

NOAA 1991-2020 normals for Alva 1W, 1.9 km from Alva, elevation 1464 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Alva 1W. 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 10 and the first fall freeze around October 28, a growing season of about 199 days.

Median at 36°F
last April 20, first October 18
Median at 32°F
last April 10, first October 28
Median at 28°F
last March 31, first November 5

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 2Apr 29Apr 26Apr 23Apr 20Apr 17Apr 14Apr 11Apr 7
32°FApr 25Apr 20Apr 16Apr 13Apr 10Apr 7Apr 4Apr 1Mar 26
28°FApr 14Apr 10Apr 6Apr 3Mar 31Mar 28Mar 24Mar 19Mar 12
24°FApr 5Mar 31Mar 27Mar 22Mar 18Mar 13Mar 9Mar 5Feb 28
20°FMar 27Mar 18Mar 13Mar 10Mar 6Mar 2Feb 27Feb 23Feb 15
16°FMar 14Mar 7Mar 3Feb 28Feb 24Feb 19Feb 14Feb 8Jan 30

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°FOct 4Oct 10Oct 14Oct 16Oct 18Oct 21Oct 23Oct 27Oct 31
32°FOct 14Oct 18Oct 21Oct 24Oct 28Oct 30Nov 2Nov 5Nov 10
28°FOct 22Oct 27Oct 30Nov 2Nov 5Nov 7Nov 10Nov 15Nov 20
24°FOct 29Nov 2Nov 6Nov 10Nov 13Nov 18Nov 21Nov 25Dec 1
20°FNov 3Nov 10Nov 15Nov 19Nov 23Nov 27Nov 30Dec 4Dec 11
16°FNov 13Nov 20Nov 26Nov 30Dec 3Dec 7Dec 12Dec 18Dec 26

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°F200194189185181177173169162
32°F221213208203199196192187181
28°F243234227223218214211205197
24°F265257251244240236230224216
20°F286279273267262256250244234
16°F312303296290284279274265256

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
4,209
Cooling degree days, base 65°F
1,908
Growing degree days, base 40°F
7,435
Growing degree days, base 45°F
6,045
Growing degree days, base 50°F
4,807
Growing degree days, base 55°F
3,706
Growing degree days, base 60°F
2,740

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January93503
February735017
March537397
April25925250
May61151556
June3390837
July05531,018
August1478942
September24261687
October21744316
November551275
December88608

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 1.9 km from Alva. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00340193 (Alva 1W). Public domain.