Monticello climate

Monticello Frost Dates and Growing Season

NOAA 1991-2020 normals for Monticello Muni AP, 3.4 km from Monticello, elevation 290 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Monticello Muni AP. 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 18 and the first fall freeze around November 12, a growing season of about 238 days.

Median at 36°F
last April 1, first November 1
Median at 32°F
last March 18, first November 12
Median at 28°F
last March 4, first November 25

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 17Apr 12Apr 7Apr 4Apr 1Mar 29Mar 24Mar 19Mar 13
32°FApr 6Mar 31Mar 26Mar 22Mar 18Mar 14Mar 10Mar 5Feb 26
28°FMar 23Mar 17Mar 12Mar 8Mar 4Mar 1Feb 25Feb 19Feb 10
24°FMar 11Mar 5Mar 1Feb 24Feb 19Feb 11Feb 4Jan 31Jan 22
20°FMar 3Feb 22Feb 12Feb 4Jan 31Jan 26Jan 18Jan 10Dec 31
16°FFeb 21Feb 6Jan 31Jan 26Jan 20Jan 13Jan 9Jan 2Dec 22

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 19Oct 23Oct 27Oct 30Nov 1Nov 4Nov 7Nov 11Nov 17
32°FOct 28Nov 1Nov 5Nov 8Nov 12Nov 15Nov 20Nov 24Dec 1
28°FNov 5Nov 10Nov 16Nov 21Nov 25Nov 30Dec 3Dec 7Dec 17
24°FNov 16Nov 25Nov 30Dec 4Dec 9Dec 15Dec 23Dec 31Jan 8
20°FDec 2Dec 11Dec 18Dec 26Jan 1Jan 5Jan 11Jan 17Jan 31
16°FDec 11Dec 21Dec 29Jan 2Jan 8Jan 13Jan 17Jan 26Feb 5

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°F237230223218214208204200192
32°F263254248243238232227221213
28°F296284277270264259252246236
24°F334321311303297289281273261
20°F365356347338333326316305293
16°F365365365365362355346335323

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
99% of years
20°F or colder
88% of years
16°F or colder
49% 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
2,634
Cooling degree days, base 65°F
2,322
Growing degree days, base 40°F
8,978
Growing degree days, base 45°F
7,359
Growing degree days, base 50°F
5,874
Growing degree days, base 55°F
4,535
Growing degree days, base 60°F
3,347

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January653257
February482488
March31124233
April12179415
May19239685
June0434883
July05441,009
August0525990
September7342784
October108108470
November34817184
December585476

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 3.4 km from Monticello. 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 USW00053919 (Monticello Muni AP). Public domain.