Hill City climate

Hill City Frost Dates and Growing Season

NOAA 1991-2020 normals for Hill City, 1.4 km from Hill City, elevation 4946 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hill City. 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 June 1 and the first fall freeze around September 10, a growing season of about 102 days.

Median at 36°F
last June 18, first September 1
Median at 32°F
last June 1, first September 10
Median at 28°F
last May 18, first September 21

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°FJul 7Jul 1Jun 26Jun 21Jun 18Jun 14Jun 10Jun 5May 31
32°FJun 19Jun 12Jun 7Jun 3Jun 1May 29May 25May 22May 18
28°FJun 1May 28May 25May 21May 18May 15May 13May 10May 6
24°FMay 19May 13May 10May 7May 6May 3May 1Apr 28Apr 24
20°FMay 8May 3Apr 30Apr 28Apr 25Apr 22Apr 19Apr 15Apr 10
16°FApr 30Apr 26Apr 23Apr 19Apr 16Apr 13Apr 9Apr 6Mar 31

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 12Aug 20Aug 25Aug 29Sep 1Sep 2Sep 5Sep 9Sep 14
32°FAug 29Sep 2Sep 5Sep 7Sep 10Sep 13Sep 17Sep 21Sep 26
28°FSep 6Sep 11Sep 15Sep 18Sep 21Sep 24Sep 28Oct 1Oct 6
24°FSep 16Sep 21Sep 25Sep 29Oct 1Oct 5Oct 8Oct 12Oct 16
20°FSep 25Oct 1Oct 5Oct 9Oct 13Oct 16Oct 19Oct 22Oct 26
16°FOct 5Oct 12Oct 16Oct 20Oct 22Oct 25Oct 28Nov 1Nov 4

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°F948883787367625646
32°F12111411010610296928676
28°F146138134130126122117111105
24°F168161156152148144140134127
20°F190182178173170166161155146
16°F210203197193189185180174167

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
7,881
Cooling degree days, base 65°F
227
Growing degree days, base 40°F
3,467
Growing degree days, base 45°F
2,496
Growing degree days, base 50°F
1,697
Growing degree days, base 55°F
1,053
Growing degree days, base 60°F
558

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,23900
February1,10700
March96004
April719015
May4473114
June17231316
July52106519
August7274468
September27913220
October656038
November95403
December1,22600

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 1.4 km from Hill City. 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 USC00393868 (Hill City). Public domain.