Pomona climate

Pomona Frost Dates and Growing Season

NOAA 1991-2020 normals for Atlantic City Intl AP, 3.4 km from Pomona, elevation 60 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Atlantic City Intl 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 April 18 and the first fall freeze around October 29, a growing season of about 190 days.

Median at 36°F
last April 30, first October 18
Median at 32°F
last April 18, first October 29
Median at 28°F
last April 5, 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 16May 11May 7May 3Apr 30Apr 27Apr 24Apr 20Apr 16
32°FMay 5Apr 30Apr 24Apr 21Apr 18Apr 15Apr 11Apr 8Apr 2
28°FApr 20Apr 16Apr 12Apr 9Apr 5Apr 2Mar 30Mar 27Mar 22
24°FApr 8Apr 2Mar 30Mar 27Mar 24Mar 21Mar 18Mar 14Mar 8
20°FMar 27Mar 22Mar 19Mar 16Mar 12Mar 8Mar 4Feb 28Feb 22
16°FMar 18Mar 12Mar 7Mar 3Feb 28Feb 24Feb 19Feb 13Feb 6

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 18Oct 20Oct 24Oct 28Nov 1
32°FOct 13Oct 18Oct 22Oct 26Oct 29Nov 1Nov 3Nov 6Nov 11
28°FOct 25Oct 31Nov 2Nov 5Nov 8Nov 11Nov 14Nov 17Nov 23
24°FNov 3Nov 8Nov 13Nov 17Nov 19Nov 23Nov 28Dec 2Dec 7
20°FNov 15Nov 20Nov 26Dec 1Dec 3Dec 7Dec 11Dec 17Dec 23
16°FDec 1Dec 4Dec 9Dec 15Dec 19Dec 23Dec 28Jan 1Jan 10

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°F190183176172167164159154147
32°F211204199194190185181175167
28°F236228223218214210205200193
24°F265257251246241236231225218
20°F292283276271267261257251242
16°F319310303298292287281276266

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
4,701
Cooling degree days, base 65°F
1,136
Growing degree days, base 40°F
6,202
Growing degree days, base 45°F
4,866
Growing degree days, base 50°F
3,695
Growing degree days, base 55°F
2,691
Growing degree days, base 60°F
1,839

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January95607
February81208
March695135
April38712142
May15561373
June23215642
July0369834
August1311775
September43144551
October27023243
November546166
December814019

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 Pomona. 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 USW00093730 (Atlantic City Intl AP). Public domain.