Overbrook climate

Overbrook Frost Dates and Growing Season

NOAA 1991-2020 normals for Pomona Lake, 15.1 km from Overbrook, elevation 1063 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Pomona Lake. 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 8 and the first fall freeze around October 31, a growing season of about 205 days.

Median at 36°F
last April 18, first October 22
Median at 32°F
last April 8, first October 31
Median at 28°F
last March 30, first November 8

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 1Apr 28Apr 24Apr 21Apr 18Apr 15Apr 13Apr 9Apr 4
32°FApr 22Apr 18Apr 14Apr 11Apr 8Apr 5Apr 2Mar 30Mar 23
28°FApr 12Apr 7Apr 4Apr 1Mar 30Mar 26Mar 22Mar 17Mar 10
24°FApr 3Mar 30Mar 25Mar 21Mar 17Mar 13Mar 9Mar 4Feb 28
20°FMar 24Mar 18Mar 13Mar 10Mar 6Mar 3Feb 28Feb 25Feb 19
16°FMar 16Mar 9Mar 5Mar 2Feb 28Feb 24Feb 20Feb 15Feb 8

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 8Oct 14Oct 18Oct 20Oct 22Oct 24Oct 26Oct 30Nov 2
32°FOct 18Oct 22Oct 26Oct 29Oct 31Nov 1Nov 4Nov 8Nov 14
28°FOct 27Oct 31Nov 2Nov 5Nov 8Nov 11Nov 14Nov 20Nov 26
24°FNov 1Nov 7Nov 12Nov 14Nov 18Nov 22Nov 26Nov 30Dec 5
20°FNov 10Nov 16Nov 21Nov 24Nov 29Dec 1Dec 5Dec 9Dec 15
16°FNov 20Nov 27Dec 1Dec 5Dec 8Dec 13Dec 18Dec 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°F205198193189185181177172166
32°F227218213209205201197192184
28°F249241235230224220215209203
24°F270262256250246241235228220
20°F289282275270266261255250241
16°F312303297290285280274268259

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
4,743
Cooling degree days, base 65°F
1,578
Growing degree days, base 40°F
6,836
Growing degree days, base 45°F
5,513
Growing degree days, base 50°F
4,327
Growing degree days, base 55°F
3,276
Growing degree days, base 60°F
2,361

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,04903
February840012
March614580
April31322215
May95115488
June5317762
July0467931
August1418882
September44195602
October25738282
November594265
December93107

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 15.1 km from Overbrook. 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 USC00146498 (Pomona Lake). Public domain.