Saint Peters climate

Saint Peters Frost Dates and Growing Season

NOAA 1991-2020 normals for St Peters 2 Se, 4.8 km from Saint Peters, elevation 575 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for St Peters 2 Se. 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 9 and the first fall freeze around October 26, a growing season of about 198 days.

Median at 36°F
last April 23, first October 17
Median at 32°F
last April 9, first October 26
Median at 28°F
last March 31, first November 5

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°FMay 8May 2Apr 30Apr 26Apr 23Apr 19Apr 16Apr 11Apr 7
32°FApr 25Apr 21Apr 17Apr 13Apr 9Apr 6Apr 3Mar 31Mar 27
28°FApr 14Apr 9Apr 5Apr 2Mar 31Mar 28Mar 23Mar 18Mar 12
24°FApr 4Mar 31Mar 28Mar 24Mar 20Mar 16Mar 13Mar 9Mar 3
20°FMar 27Mar 21Mar 16Mar 13Mar 9Mar 6Mar 3Feb 27Feb 20
16°FMar 17Mar 12Mar 7Mar 4Mar 1Feb 27Feb 21Feb 15Feb 7

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 4Oct 8Oct 12Oct 15Oct 17Oct 19Oct 21Oct 23Oct 27
32°FOct 14Oct 18Oct 21Oct 24Oct 26Oct 28Oct 31Nov 3Nov 7
28°FOct 25Oct 30Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17Nov 22
24°FNov 3Nov 7Nov 10Nov 14Nov 18Nov 22Nov 26Dec 1Dec 6
20°FNov 11Nov 17Nov 21Nov 25Nov 29Dec 1Dec 6Dec 11Dec 19
16°FNov 21Nov 27Dec 1Dec 6Dec 10Dec 14Dec 20Dec 24Dec 30

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°F193187183178174170166162156
32°F219212207202198194190186178
28°F243236230226221217212207200
24°F267259253248243239234227220
20°F289280274269264259253246239
16°F313302296290285280275268259

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
4,863
Cooling degree days, base 65°F
1,357
Growing degree days, base 40°F
6,545
Growing degree days, base 45°F
5,230
Growing degree days, base 50°F
4,056
Growing degree days, base 55°F
3,021
Growing degree days, base 60°F
2,122

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,07704
February844015
March644672
April31524211
May109106465
June9274715
July1397862
August3353815
September49167569
October27926251
November604366
December928012

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 4.8 km from Saint Peters. 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 USC00237475 (St Peters 2 Se). Public domain.