Jerome climate

Jerome Frost Dates and Growing Season

NOAA 1991-2020 normals for Jerome, 0.9 km from Jerome, elevation 3740 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jerome. 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 2 and the first fall freeze around October 14, a growing season of about 166 days.

Median at 36°F
last May 15, first October 3
Median at 32°F
last May 2, first October 14
Median at 28°F
last April 14, first October 27

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 8May 31May 25May 19May 15May 12May 8May 4Apr 30
32°FMay 30May 16May 10May 5May 2Apr 29Apr 26Apr 22Apr 15
28°FMay 10Apr 30Apr 25Apr 19Apr 14Apr 10Apr 6Apr 1Mar 24
24°FApr 21Apr 9Apr 3Mar 30Mar 24Mar 19Mar 14Mar 9Mar 3
20°FApr 1Mar 18Mar 12Mar 8Mar 5Mar 1Feb 26Feb 20Feb 12
16°FMar 8Mar 3Feb 28Feb 25Feb 19Feb 15Feb 11Feb 5Jan 27

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 17Sep 24Sep 28Oct 1Oct 3Oct 6Oct 9Oct 13Oct 17
32°FSep 30Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 24Oct 29
28°FOct 13Oct 18Oct 22Oct 25Oct 27Oct 30Nov 1Nov 5Nov 11
24°FOct 22Oct 28Oct 31Nov 3Nov 6Nov 10Nov 13Nov 18Nov 23
20°FOct 31Nov 5Nov 9Nov 13Nov 17Nov 21Nov 24Nov 27Dec 2
16°FNov 8Nov 14Nov 19Nov 23Nov 26Nov 30Dec 3Dec 8Dec 16

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°F160153148142138133127120110
32°F188180175170166161155148136
28°F217209203198194189183177166
24°F255246239233227220214206196
20°F283273267261256251245236224
16°F310301294288282275270264255

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
6,177
Cooling degree days, base 65°F
776
Growing degree days, base 40°F
4,886
Growing degree days, base 45°F
3,749
Growing degree days, base 50°F
2,783
Growing degree days, base 55°F
1,975
Growing degree days, base 60°F
1,309

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12700
February89500
March738011
April517162
May27022243
June93109469
July10312767
August14258708
September12470402
October4534112
November81609
December1,12000

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 0.9 km from Jerome. 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 USC00104670 (Jerome). Public domain.