Caldwell climate

Caldwell Frost Dates and Growing Season

NOAA 1991-2020 normals for Somerville Dam, 26.1 km from Caldwell, elevation 263 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Somerville Dam. 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 March 18 and the first fall freeze around November 9, a growing season of about 238 days.

Median at 36°F
last April 1, first November 1
Median at 32°F
last March 18, first November 9
Median at 28°F
last March 5, first November 23

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°FApr 20Apr 13Apr 8Apr 4Apr 1Mar 28Mar 24Mar 19Mar 12
32°FApr 6Apr 1Mar 27Mar 22Mar 18Mar 14Mar 9Mar 3Feb 25
28°FMar 24Mar 17Mar 12Mar 8Mar 5Mar 1Feb 24Feb 16Feb 4
24°FMar 13Mar 7Mar 1Feb 23Feb 16Feb 7Feb 1Jan 27Jan 17
20°FMar 1Feb 17Feb 7Jan 31Jan 27Jan 22Jan 16Jan 8Dec 31
16°FFeb 13Feb 2Jan 28Jan 23Jan 18Jan 11Jan 7Jan 4Dec 27

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 19Oct 23Oct 27Oct 29Nov 1Nov 3Nov 6Nov 11Nov 17
32°FOct 26Oct 31Nov 3Nov 6Nov 9Nov 14Nov 18Nov 24Nov 30
28°FNov 3Nov 9Nov 14Nov 19Nov 23Nov 27Dec 2Dec 6Dec 14
24°FNov 14Nov 22Nov 28Dec 2Dec 7Dec 13Dec 23Jan 1Jan 9
20°FNov 26Dec 5Dec 13Dec 24Jan 1Jan 4Jan 9Jan 15Jan 27
16°FDec 11Dec 25Jan 1Jan 4Jan 6Jan 11Jan 16Jan 23Feb 3

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°F239230224219213209204199192
32°F267257250243238232227219211
28°F298286277270263257251243234
24°F339325313305298290280271257
20°F365359349342335329320308296
16°F365365365365365363354344333

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
99% of years
20°F or colder
85% of years
16°F or colder
43% 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
1,933
Cooling degree days, base 65°F
2,690
Growing degree days, base 40°F
9,943
Growing degree days, base 45°F
8,229
Growing degree days, base 50°F
6,621
Growing degree days, base 55°F
5,153
Growing degree days, base 60°F
3,840

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January514493
February3607141
March21838312
April70108490
May8293750
June0473922
July05741,039
August05861,051
September4397843
October63164569
November24139283
December4569129

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 26.1 km from Caldwell. 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 USC00418446 (Somerville Dam). Public domain.