Roosevelt climate

Roosevelt Frost Dates and Growing Season

NOAA 1991-2020 normals for Roosevelt Radio, 2.9 km from Roosevelt, elevation 5014 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Roosevelt Radio. 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 23 and the first fall freeze around September 22, a growing season of about 121 days.

Median at 36°F
last June 8, first September 12
Median at 32°F
last May 23, first September 22
Median at 28°F
last May 8, first October 2

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 27Jun 20Jun 15Jun 11Jun 8Jun 5Jun 2May 30May 25
32°FJun 9Jun 3May 31May 27May 23May 20May 17May 13May 9
28°FMay 25May 19May 15May 11May 8May 6May 3May 1Apr 27
24°FMay 11May 6May 3Apr 30Apr 28Apr 25Apr 22Apr 18Apr 14
20°FApr 30Apr 25Apr 21Apr 18Apr 15Apr 11Apr 8Apr 4Mar 31
16°FApr 18Apr 11Apr 7Apr 3Mar 31Mar 28Mar 24Mar 18Mar 12

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 30Sep 4Sep 7Sep 9Sep 12Sep 15Sep 17Sep 21Sep 25
32°FSep 8Sep 13Sep 17Sep 19Sep 22Sep 25Sep 27Sep 30Oct 3
28°FSep 20Sep 24Sep 27Sep 30Oct 2Oct 4Oct 6Oct 9Oct 15
24°FSep 30Oct 3Oct 6Oct 10Oct 13Oct 16Oct 19Oct 23Oct 27
20°FOct 9Oct 15Oct 18Oct 21Oct 24Oct 26Oct 30Nov 2Nov 5
16°FOct 19Oct 24Oct 27Oct 31Nov 2Nov 4Nov 7Nov 10Nov 14

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°F114107102989490858072
32°F13913212812412111611210799
28°F163157153149145141137133125
24°F187180176172168163159154148
20°F210203199194190186182177172
16°F236227221217213208204199192

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
7,327
Cooling degree days, base 65°F
511
Growing degree days, base 40°F
4,462
Growing degree days, base 45°F
3,392
Growing degree days, base 50°F
2,465
Growing degree days, base 55°F
1,676
Growing degree days, base 60°F
1,021

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,50800
February1,11700
March80904
April530047
May2628231
June6081471
July3233694
August10167622
September14623334
October532062
November95301
December1,39800

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 2.9 km from Roosevelt. 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 USC00427395 (Roosevelt Radio). Public domain.