Saint Johns climate

Saint Johns Frost Dates and Growing Season

NOAA 1991-2020 normals for Saint Johns, 1.2 km from Saint Johns, elevation 743 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Saint Johns. 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 28 and the first fall freeze around October 24, a growing season of about 179 days.

Median at 36°F
last May 7, first October 11
Median at 32°F
last April 28, first October 24
Median at 28°F
last April 15, 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 23May 18May 13May 10May 7May 4May 1Apr 28Apr 23
32°FMay 12May 7May 3Apr 30Apr 28Apr 25Apr 21Apr 17Apr 12
28°FApr 30Apr 25Apr 21Apr 18Apr 15Apr 11Apr 8Apr 5Apr 1
24°FApr 18Apr 11Apr 8Apr 5Apr 3Apr 1Mar 30Mar 25Mar 19
20°FApr 7Apr 3Mar 31Mar 28Mar 25Mar 22Mar 18Mar 15Mar 10
16°FMar 31Mar 26Mar 22Mar 19Mar 16Mar 14Mar 10Mar 7Mar 2

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 28Oct 2Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 25
32°FOct 7Oct 13Oct 17Oct 21Oct 24Oct 27Oct 30Nov 2Nov 7
28°FOct 22Oct 27Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15Nov 20
24°FNov 1Nov 6Nov 10Nov 13Nov 17Nov 20Nov 24Nov 28Dec 3
20°FNov 11Nov 16Nov 20Nov 25Nov 28Dec 1Dec 4Dec 10Dec 16
16°FNov 20Nov 27Dec 1Dec 4Dec 7Dec 12Dec 16Dec 21Dec 28

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°F176171166161158153149144136
32°F199193187183179175171165158
28°F224217211208203199194189182
24°F249243237231227223218214207
20°F273264258253248244240234227
16°F292285279274268264258252245

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
6,508
Cooling degree days, base 65°F
745
Growing degree days, base 40°F
4,980
Growing degree days, base 45°F
3,868
Growing degree days, base 50°F
2,891
Growing degree days, base 55°F
2,043
Growing degree days, base 60°F
1,323

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,26600
February1,09701
March934118
April554471
May24046291
June44158564
July7247705
August14200651
September11180421
October40810145
November748021
December1,08302

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 1.2 km from Saint Johns. 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 USC00207280 (Saint Johns). Public domain.