Pomona climate

Pomona Frost Dates and Growing Season

NOAA 1991-2020 normals for West Plains Muni AP, 1.6 km from Pomona, elevation 1223 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for West Plains 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 April 8 and the first fall freeze around October 25, a growing season of about 199 days.

Median at 36°F
last April 23, first October 16
Median at 32°F
last April 8, first October 25
Median at 28°F
last March 28, first November 4

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 9May 4Apr 30Apr 27Apr 23Apr 20Apr 16Apr 10Apr 5
32°FApr 26Apr 20Apr 16Apr 12Apr 8Apr 5Apr 1Mar 29Mar 23
28°FApr 14Apr 7Apr 3Mar 31Mar 28Mar 24Mar 21Mar 16Mar 10
24°FApr 2Mar 28Mar 24Mar 20Mar 16Mar 12Mar 8Mar 4Feb 27
20°FMar 24Mar 17Mar 12Mar 9Mar 5Mar 2Feb 27Feb 22Feb 15
16°FMar 15Mar 7Mar 3Feb 28Feb 24Feb 20Feb 14Feb 9Jan 31

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 3Oct 8Oct 11Oct 14Oct 16Oct 19Oct 21Oct 24Oct 28
32°FOct 14Oct 18Oct 21Oct 23Oct 25Oct 29Nov 1Nov 3Nov 8
28°FOct 23Oct 28Oct 31Nov 2Nov 4Nov 7Nov 11Nov 16Nov 23
24°FNov 2Nov 5Nov 9Nov 12Nov 15Nov 20Nov 25Nov 30Dec 5
20°FNov 9Nov 15Nov 20Nov 25Nov 29Dec 2Dec 6Dec 11Dec 17
16°FNov 20Nov 28Dec 2Dec 7Dec 11Dec 15Dec 19Dec 24Jan 1

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°F197190184180176171167162155
32°F220212208203199194190184177
28°F245237231226221216212207199
24°F270261255250244239235229220
20°F295285279273267263256251242
16°F321311303297291286280273261

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
4,264
Cooling degree days, base 65°F
1,369
Growing degree days, base 40°F
6,846
Growing degree days, base 45°F
5,451
Growing degree days, base 50°F
4,206
Growing degree days, base 55°F
3,111
Growing degree days, base 60°F
2,164

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January945010
February731023
March545490
April25324252
May83102485
June5271715
July0400865
August1371835
September40163573
October25332271
November554272
December852015

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 1.6 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 USW00053901 (West Plains Muni AP). Public domain.