Middleton climate

Middleton Frost Dates and Growing Season

NOAA 1991-2020 normals for Bolivar Wtr Wks, 23.7 km from Middleton, elevation 455 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bolivar Wtr Wks. 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 April 3 and the first fall freeze around October 30, a growing season of about 210 days.

Median at 36°F
last April 14, first October 21
Median at 32°F
last April 3, first October 30
Median at 28°F
last March 21, first November 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°FApr 30Apr 25Apr 22Apr 18Apr 14Apr 11Apr 9Apr 5Mar 31
32°FApr 19Apr 13Apr 9Apr 6Apr 3Mar 31Mar 28Mar 23Mar 17
28°FApr 7Apr 2Mar 29Mar 25Mar 21Mar 17Mar 13Mar 9Mar 2
24°FMar 26Mar 20Mar 15Mar 11Mar 8Mar 3Feb 28Feb 24Feb 18
20°FMar 15Mar 9Mar 3Feb 28Feb 24Feb 19Feb 14Feb 7Jan 31
16°FMar 5Feb 26Feb 19Feb 12Feb 6Feb 1Jan 28Jan 21Jan 9

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 7Oct 12Oct 16Oct 19Oct 21Oct 23Oct 26Oct 29Nov 1
32°FOct 17Oct 22Oct 25Oct 28Oct 30Nov 1Nov 4Nov 7Nov 13
28°FOct 29Nov 1Nov 4Nov 6Nov 9Nov 12Nov 16Nov 20Nov 27
24°FNov 5Nov 8Nov 13Nov 17Nov 21Nov 25Nov 30Dec 3Dec 10
20°FNov 11Nov 19Nov 26Dec 1Dec 4Dec 9Dec 15Dec 22Dec 30
16°FNov 27Dec 4Dec 11Dec 19Dec 25Dec 30Jan 4Jan 10Jan 17

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°F209202197193189184180175168
32°F232224219214210205201196188
28°F260250244239234229224217209
24°F286276269264259254248243233
20°F317307300292285279273266257
16°F352338331323315309302294282

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
96% 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
3,595
Cooling degree days, base 65°F
1,652
Growing degree days, base 40°F
7,580
Growing degree days, base 45°F
6,099
Growing degree days, base 50°F
4,758
Growing degree days, base 55°F
3,570
Growing degree days, base 60°F
2,535

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January820027
February637141
March4578134
April20143312
May52148561
June2327775
July0442907
August0408873
September22220648
October19351339
November4805104
December732137

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 23.7 km from Middleton. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00400876 (Bolivar Wtr Wks). Public domain.