Richland climate

Richland Frost Dates and Growing Season

NOAA 1991-2020 normals for Gull Lake Biological Stn, 6.1 km from Richland, elevation 925 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Gull Lake Biological Stn. 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 29 and the first fall freeze around October 20, a growing season of about 173 days.

Median at 36°F
last May 11, first October 6
Median at 32°F
last April 29, first October 20
Median at 28°F
last April 15, first November 3

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 24May 19May 15May 11May 7May 3Apr 30Apr 25
32°FMay 18May 10May 6May 2Apr 29Apr 26Apr 22Apr 18Apr 12
28°FMay 4Apr 27Apr 23Apr 19Apr 15Apr 12Apr 9Apr 6Apr 1
24°FApr 20Apr 15Apr 10Apr 7Apr 4Apr 2Mar 31Mar 27Mar 21
20°FApr 9Apr 4Apr 1Mar 29Mar 26Mar 23Mar 19Mar 15Mar 10
16°FMar 31Mar 26Mar 22Mar 19Mar 16Mar 13Mar 10Mar 6Feb 27

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 22Sep 27Oct 1Oct 4Oct 6Oct 10Oct 12Oct 16Oct 21
32°FOct 4Oct 10Oct 13Oct 17Oct 20Oct 23Oct 27Oct 31Nov 3
28°FOct 20Oct 25Oct 29Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17
24°FNov 3Nov 7Nov 10Nov 13Nov 16Nov 19Nov 23Nov 27Dec 2
20°FNov 9Nov 15Nov 20Nov 24Nov 28Dec 1Dec 4Dec 8Dec 15
16°FNov 21Nov 28Dec 1Dec 4Dec 7Dec 10Dec 15Dec 19Dec 25

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°F168162156151147141138131122
32°F195188182177173168163158148
28°F220212207204200196191185179
24°F248238233228224219215210204
20°F270260255250245241235230221
16°F290282276271266262257251243

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
6,089
Cooling degree days, base 65°F
808
Growing degree days, base 40°F
5,266
Growing degree days, base 45°F
4,108
Growing degree days, base 50°F
3,083
Growing degree days, base 55°F
2,193
Growing degree days, base 60°F
1,430

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,22801
February1,04402
March841127
April4757104
May18958347
June29173594
July5261721
August12212665
September10687434
October37710159
November716029
December1,06602

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 6.1 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 USC00203504 (Gull Lake Biological Stn). Public domain.