Hays climate

Hays Frost Dates and Growing Season

NOAA 1991-2020 normals for Zortman, 14.9 km from Hays, elevation 4035 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Zortman. 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 18 and the first fall freeze around September 23, a growing season of about 126 days.

Median at 36°F
last May 31, first September 12
Median at 32°F
last May 18, first September 23
Median at 28°F
last May 5, 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 20Jun 11Jun 6Jun 2May 31May 28May 25May 22May 18
32°FJun 1May 28May 24May 21May 18May 15May 11May 8May 4
28°FMay 20May 14May 9May 7May 5May 2Apr 30Apr 27Apr 20
24°FMay 8May 3Apr 30Apr 28Apr 24Apr 21Apr 17Apr 13Apr 8
20°FApr 29Apr 24Apr 19Apr 15Apr 12Apr 9Apr 6Apr 2Mar 27
16°FApr 21Apr 14Apr 10Apr 6Apr 3Mar 31Mar 27Mar 20Mar 13

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 26Sep 1Sep 5Sep 9Sep 12Sep 15Sep 19Sep 22Sep 26
32°FSep 7Sep 14Sep 18Sep 21Sep 23Sep 25Sep 28Oct 1Oct 5
28°FSep 17Sep 24Sep 27Sep 30Oct 2Oct 5Oct 8Oct 12Oct 17
24°FSep 26Oct 1Oct 5Oct 8Oct 12Oct 15Oct 19Oct 24Oct 30
20°FOct 1Oct 9Oct 15Oct 19Oct 23Oct 27Oct 30Nov 3Nov 9
16°FOct 10Oct 18Oct 24Oct 28Nov 1Nov 4Nov 8Nov 12Nov 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°F12211511010610196908372
32°F145140135130126122117110103
28°F170162157153149145141135127
24°F194185180174169165160154147
20°F218207200194189184179173162
16°F235227220214209203197190179

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
8,163
Cooling degree days, base 65°F
260
Growing degree days, base 40°F
3,430
Growing degree days, base 45°F
2,466
Growing degree days, base 50°F
1,675
Growing degree days, base 55°F
1,047
Growing degree days, base 60°F
576

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27401
February1,13502
March1,01705
April732019
May4683110
June21718262
July68110507
August84106490
September30623220
October678149
November95609
December1,22700

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 14.9 km from Hays. 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 USC00249900 (Zortman). Public domain.