Hanson County climate

Hanson County Frost Dates and Growing Season

NOAA 1991-2020 normals for Alexandria, 2.8 km from Hanson County, elevation 1365 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Alexandria. 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 8 and the first fall freeze around September 29, a growing season of about 143 days.

Median at 36°F
last May 18, first September 22
Median at 32°F
last May 8, first September 29
Median at 28°F
last April 30, first October 7

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 31May 27May 23May 20May 18May 15May 13May 9May 5
32°FMay 21May 16May 14May 10May 8May 5May 3Apr 30Apr 27
28°FMay 13May 8May 5May 3Apr 30Apr 29Apr 25Apr 21Apr 15
24°FMay 4Apr 30Apr 27Apr 24Apr 21Apr 17Apr 14Apr 10Apr 6
20°FApr 27Apr 21Apr 17Apr 13Apr 10Apr 7Apr 4Apr 1Mar 26
16°FApr 18Apr 11Apr 8Apr 4Apr 2Mar 30Mar 26Mar 20Mar 14

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 9Sep 13Sep 16Sep 19Sep 22Sep 24Sep 27Sep 29Oct 2
32°FSep 17Sep 21Sep 24Sep 27Sep 29Oct 1Oct 3Oct 7Oct 11
28°FSep 24Sep 29Oct 2Oct 4Oct 7Oct 10Oct 13Oct 16Oct 20
24°FOct 2Oct 6Oct 10Oct 14Oct 17Oct 20Oct 23Oct 26Oct 30
20°FOct 12Oct 17Oct 21Oct 23Oct 25Oct 28Oct 31Nov 3Nov 7
16°FOct 22Oct 26Oct 30Nov 1Nov 3Nov 5Nov 8Nov 13Nov 18

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°F143138133129126123119114106
32°F160154150147143140136131126
28°F179173169165161157154149143
24°F200193188183180175171166159
20°F219211206202198194190186178
16°F239230224220216212207203195

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
7,874
Cooling degree days, base 65°F
626
Growing degree days, base 40°F
4,541
Growing degree days, base 45°F
3,521
Growing degree days, base 50°F
2,614
Growing degree days, base 55°F
1,822
Growing degree days, base 60°F
1,157

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,53300
February1,25201
March1,016013
April610262
May27928253
June53126524
July12232685
August26169608
September15965367
October552594
November98108
December1,40300

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 2.8 km from Hanson County. 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 USC00390128 (Alexandria). Public domain.