Harrison climate

Harrison Frost Dates and Growing Season

NOAA 1991-2020 normals for Harrison, 0.2 km from Harrison, elevation 4850 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Harrison. 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 20 and the first fall freeze around September 21, a growing season of about 121 days.

Median at 36°F
last May 31, first September 12
Median at 32°F
last May 20, first September 21
Median at 28°F
last May 9, first October 1

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 16Jun 10Jun 6Jun 3May 31May 29May 26May 22May 17
32°FJun 5May 31May 27May 24May 20May 18May 15May 12May 8
28°FMay 23May 18May 15May 12May 9May 7May 5May 2Apr 29
24°FMay 13May 8May 6May 3May 1Apr 28Apr 25Apr 21Apr 16
20°FMay 5Apr 30Apr 27Apr 24Apr 20Apr 17Apr 14Apr 10Apr 5
16°FApr 27Apr 21Apr 17Apr 13Apr 10Apr 7Apr 4Mar 31Mar 24

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°FAug 27Sep 1Sep 6Sep 9Sep 12Sep 15Sep 18Sep 21Sep 25
32°FSep 4Sep 10Sep 14Sep 18Sep 21Sep 24Sep 26Sep 30Oct 5
28°FSep 15Sep 20Sep 25Sep 28Oct 1Oct 4Oct 7Oct 10Oct 15
24°FSep 24Sep 29Oct 3Oct 7Oct 10Oct 14Oct 16Oct 19Oct 23
20°FOct 1Oct 9Oct 14Oct 17Oct 19Oct 22Oct 25Oct 28Nov 2
16°FOct 14Oct 19Oct 22Oct 25Oct 28Oct 31Nov 3Nov 7Nov 12

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°F12011411010610198948982
32°F141135130125121117113108100
28°F160155150146142138134129121
24°F181174169165162157153148140
20°F201193188183180175171165159
16°F221214208203198194189182177

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
7,834
Cooling degree days, base 65°F
422
Growing degree days, base 40°F
3,909
Growing degree days, base 45°F
2,935
Growing degree days, base 50°F
2,107
Growing degree days, base 55°F
1,415
Growing degree days, base 60°F
850

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,29700
February1,12700
March96606
April710028
May4216145
June13059387
July23186628
August42140564
September23131285
October639059
November97706
December1,27200

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 0.2 km from Harrison. 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 USC00253615 (Harrison). Public domain.