Richland climate

Richland Frost Dates and Growing Season

NOAA 1991-2020 normals for Richland, 3.3 km from Richland, elevation 373 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Richland. 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 6 and the first fall freeze around October 24, a growing season of about 200 days.

Median at 36°F
last April 25, first October 14
Median at 32°F
last April 6, first October 24
Median at 28°F
last March 18, first November 4

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

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 30Oct 5Oct 7Oct 11Oct 14Oct 16Oct 19Oct 22Oct 27
32°FOct 10Oct 14Oct 18Oct 21Oct 24Oct 26Oct 30Nov 3Nov 8
28°FOct 20Oct 26Oct 29Nov 1Nov 4Nov 7Nov 11Nov 16Nov 23
24°FOct 29Nov 3Nov 8Nov 12Nov 16Nov 21Nov 25Dec 1Dec 9
20°FNov 8Nov 15Nov 23Nov 28Dec 3Dec 7Dec 13Dec 22Jan 1
16°FNov 17Nov 27Dec 4Dec 9Dec 14Dec 20Dec 28Jan 4Jan 19

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°F192185180175171167164159153
32°F221215210204200195191186179
28°F255246239234229225220213205
24°F294280274268262256251244236
20°F337324314306298290281272261
16°F365356344338330322314306291

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
99% of years
16°F or colder
89% 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
4,935
Cooling degree days, base 65°F
795
Growing degree days, base 40°F
5,611
Growing degree days, base 45°F
4,268
Growing degree days, base 50°F
3,125
Growing degree days, base 55°F
2,177
Growing degree days, base 60°F
1,400

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January93902
February73404
March586027
April3602120
May15534346
June40109519
July3302764
August5270730
September7075455
October3764141
November711015
December95602

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 3.3 km from Richland. 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 USC00457015 (Richland). Public domain.