Hartman climate

Hartman Frost Dates and Growing Season

NOAA 1991-2020 normals for Subiaco, 14.6 km from Hartman, elevation 500 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Subiaco. 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 March 28 and the first fall freeze around November 5, a growing season of about 223 days.

Median at 36°F
last April 8, first October 27
Median at 32°F
last March 28, first November 5
Median at 28°F
last March 14, first November 15

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°FApr 25Apr 20Apr 16Apr 11Apr 8Apr 6Apr 3Mar 30Mar 24
32°FApr 14Apr 7Apr 4Mar 31Mar 28Mar 24Mar 19Mar 15Mar 8
28°FApr 1Mar 27Mar 21Mar 17Mar 14Mar 9Mar 5Mar 1Feb 24
24°FMar 20Mar 14Mar 9Mar 5Mar 2Feb 27Feb 23Feb 17Feb 9
20°FMar 10Mar 4Feb 28Feb 23Feb 17Feb 12Feb 7Jan 31Jan 24
16°FMar 1Feb 19Feb 12Feb 6Feb 1Jan 29Jan 21Jan 14Jan 1

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 14Oct 19Oct 22Oct 25Oct 27Oct 30Nov 1Nov 5Nov 9
32°FOct 23Oct 28Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15Nov 22
28°FNov 1Nov 5Nov 8Nov 11Nov 15Nov 20Nov 24Nov 30Dec 4
24°FNov 8Nov 14Nov 19Nov 25Nov 30Dec 2Dec 7Dec 12Dec 21
20°FNov 20Nov 29Dec 3Dec 9Dec 14Dec 21Dec 26Jan 2Jan 9
16°FDec 3Dec 11Dec 20Dec 26Jan 1Jan 4Jan 8Jan 14Jan 26

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°F221214209205201197193188181
32°F247239233228223220215210202
28°F272263258252247242236231223
24°F301292284277271266260253244
20°F331321312305298291285276266
16°F362350341334328321314306295

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
91% 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
3,446
Cooling degree days, base 65°F
1,914
Growing degree days, base 40°F
7,940
Growing degree days, base 45°F
6,440
Growing degree days, base 50°F
5,090
Growing degree days, base 55°F
3,887
Growing degree days, base 60°F
2,824

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January817120
February617141
March4289145
April18143328
May39172599
June1371820
July0510975
August0476941
September15258693
October15966383
November4557115
December734131

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 14.6 km from Hartman. 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 USC00036928 (Subiaco). Public domain.