Selby climate

Selby Frost Dates and Growing Season

NOAA 1991-2020 normals for Selby, 0.5 km from Selby, elevation 1908 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Selby. 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 8 and the first fall freeze around October 1, a growing season of about 145 days.

Median at 36°F
last May 18, first September 25
Median at 32°F
last May 8, first October 1
Median at 28°F
last April 30, first October 9

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 30May 26May 23May 21May 18May 15May 12May 10May 4
32°FMay 21May 17May 14May 11May 8May 6May 3Apr 30Apr 26
28°FMay 13May 8May 5May 2Apr 30Apr 27Apr 24Apr 20Apr 15
24°FMay 3Apr 30Apr 26Apr 23Apr 20Apr 17Apr 14Apr 11Apr 6
20°FApr 27Apr 22Apr 18Apr 15Apr 12Apr 9Apr 6Apr 2Mar 29
16°FApr 20Apr 14Apr 9Apr 6Apr 4Apr 1Mar 29Mar 23Mar 16

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 12Sep 16Sep 19Sep 22Sep 25Sep 27Sep 29Oct 1Oct 6
32°FSep 19Sep 24Sep 27Sep 29Oct 1Oct 4Oct 6Oct 10Oct 14
28°FSep 25Sep 30Oct 2Oct 5Oct 9Oct 12Oct 15Oct 18Oct 22
24°FOct 2Oct 7Oct 11Oct 15Oct 18Oct 21Oct 24Oct 28Nov 1
20°FOct 9Oct 16Oct 20Oct 23Oct 27Oct 30Nov 1Nov 5Nov 11
16°FOct 20Oct 26Oct 30Nov 1Nov 4Nov 7Nov 10Nov 14Nov 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°F147141136132128125121117111
32°F164158154149145141138132125
28°F182175170166162159155150143
24°F201193187184179175170166160
20°F217210205200196192187182175
16°F236229223218214209205199192

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
8,337
Cooling degree days, base 65°F
623
Growing degree days, base 40°F
4,358
Growing degree days, base 45°F
3,379
Growing degree days, base 50°F
2,513
Growing degree days, base 55°F
1,759
Growing degree days, base 60°F
1,125

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,59300
February1,32600
March1,08807
April663147
May31222227
June70106487
July14238688
August28191628
September18362346
October601479
November1,02904
December1,43100

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 0.5 km from Selby. 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 USC00397545 (Selby). Public domain.