Sentinel climate

Sentinel Frost Dates and Growing Season

NOAA 1991-2020 normals for Clinton Sherman AP, 7.6 km from Sentinel, elevation 1922 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Clinton Sherman AP. 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 5 and the first fall freeze around November 4, a growing season of about 210 days.

Median at 36°F
last April 16, first October 27
Median at 32°F
last April 5, first November 4
Median at 28°F
last March 24, first November 12

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 1Apr 27Apr 22Apr 19Apr 16Apr 13Apr 9Apr 5Apr 1
32°FApr 22Apr 16Apr 12Apr 9Apr 5Apr 2Mar 31Mar 26Mar 19
28°FApr 12Apr 5Apr 1Mar 29Mar 24Mar 19Mar 14Mar 9Mar 3
24°FApr 1Mar 25Mar 19Mar 13Mar 10Mar 6Mar 2Feb 27Feb 20
20°FMar 21Mar 11Mar 6Mar 2Feb 28Feb 23Feb 18Feb 11Feb 2
16°FMar 7Mar 1Feb 24Feb 17Feb 12Feb 6Jan 31Jan 24Jan 11

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°FOct 13Oct 18Oct 22Oct 25Oct 27Oct 30Nov 1Nov 5Nov 10
32°FOct 21Oct 25Oct 29Nov 1Nov 4Nov 7Nov 10Nov 14Nov 19
28°FOct 27Nov 1Nov 5Nov 9Nov 12Nov 16Nov 19Nov 23Nov 30
24°FNov 2Nov 9Nov 14Nov 19Nov 22Nov 26Dec 1Dec 4Dec 11
20°FNov 12Nov 21Nov 25Nov 30Dec 4Dec 8Dec 13Dec 19Dec 29
16°FNov 25Dec 2Dec 7Dec 13Dec 18Dec 25Jan 1Jan 7Jan 18

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°F213206200196192187182178172
32°F234226220215210206202196187
28°F255248242236231225220214205
24°F283274266260254250244237228
20°F312301294287281275268260251
16°F346334324317310304298290276

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
98% 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
3,752
Cooling degree days, base 65°F
1,981
Growing degree days, base 40°F
7,782
Growing degree days, base 45°F
6,310
Growing degree days, base 50°F
5,000
Growing degree days, base 55°F
3,846
Growing degree days, base 60°F
2,840

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January829012
February656130
March4636127
April24031271
May60168575
June1396844
July05501,015
August0502967
September19262693
October19062358
November503391
December790016

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 7.6 km from Sentinel. 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 USW00003932 (Clinton Sherman AP). Public domain.