Richardton climate

Richardton Frost Dates and Growing Season

NOAA 1991-2020 normals for Richardton Abbey, 0.6 km from Richardton, elevation 2470 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Richardton Abbey. 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 9 and the first fall freeze around October 1, a growing season of about 145 days.

Median at 36°F
last May 19, first September 24
Median at 32°F
last May 9, first October 1
Median at 28°F
last April 30, first October 10

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 1May 28May 24May 21May 19May 17May 14May 11May 7
32°FMay 23May 19May 15May 12May 9May 7May 4May 1Apr 28
28°FMay 12May 8May 5May 2Apr 30Apr 28Apr 24Apr 20Apr 16
24°FMay 2Apr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 10Apr 6
20°FApr 24Apr 20Apr 17Apr 14Apr 11Apr 8Apr 5Apr 2Mar 28
16°FApr 18Apr 13Apr 10Apr 6Apr 4Apr 1Mar 29Mar 24Mar 18

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 10Sep 16Sep 18Sep 21Sep 24Sep 26Sep 28Oct 1Oct 5
32°FSep 18Sep 24Sep 27Sep 29Oct 1Oct 4Oct 7Oct 10Oct 15
28°FSep 27Oct 1Oct 4Oct 7Oct 10Oct 13Oct 16Oct 20Oct 23
24°FOct 4Oct 9Oct 13Oct 15Oct 18Oct 21Oct 25Oct 28Nov 1
20°FOct 13Oct 18Oct 22Oct 26Oct 29Oct 31Nov 3Nov 6Nov 12
16°FOct 22Oct 27Oct 30Nov 2Nov 5Nov 8Nov 11Nov 15Nov 20

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°F143137133130127123118115108
32°F162156152148145141136131124
28°F182175170167163159155150144
24°F201194190185182177174169163
20°F219213207203199195191186179
16°F236228222218213210205200193

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
8,359
Cooling degree days, base 65°F
507
Growing degree days, base 40°F
4,122
Growing degree days, base 45°F
3,151
Growing degree days, base 50°F
2,301
Growing degree days, base 55°F
1,570
Growing degree days, base 60°F
967

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,53300
February1,29200
March1,08005
April676139
May33614201
June9771427
July24197639
August35178608
September20344314
October632265
November1,04005
December1,41200

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 0.6 km from Richardton. 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 USC00327530 (Richardton Abbey). Public domain.