Trinity climate

Trinity Frost Dates and Growing Season

NOAA 1991-2020 normals for High Pt, 8.3 km from Trinity, elevation 900 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for High Pt. 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 30 and the first fall freeze around November 5, a growing season of about 220 days.

Median at 36°F
last April 10, first October 27
Median at 32°F
last March 30, first November 5
Median at 28°F
last March 18, first November 16

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 30Apr 22Apr 17Apr 14Apr 10Apr 7Apr 4Apr 1Mar 28
32°FApr 15Apr 8Apr 5Apr 1Mar 30Mar 26Mar 24Mar 19Mar 13
28°FApr 1Mar 28Mar 25Mar 21Mar 18Mar 15Mar 11Mar 7Mar 1
24°FMar 24Mar 19Mar 14Mar 10Mar 6Mar 3Feb 28Feb 22Feb 12
20°FMar 15Mar 8Mar 2Feb 27Feb 22Feb 15Feb 7Jan 31Jan 23
16°FMar 4Feb 26Feb 16Feb 7Feb 1Jan 28Jan 23Jan 17Jan 7

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 12Oct 17Oct 21Oct 24Oct 27Oct 30Nov 1Nov 4Nov 9
32°FOct 21Oct 27Oct 31Nov 2Nov 5Nov 7Nov 11Nov 15Nov 21
28°FNov 1Nov 5Nov 9Nov 12Nov 16Nov 20Nov 24Nov 29Dec 5
24°FNov 10Nov 16Nov 22Nov 26Dec 1Dec 4Dec 9Dec 17Dec 27
20°FNov 24Dec 2Dec 7Dec 13Dec 18Dec 26Jan 1Jan 6Jan 15
16°FDec 8Dec 15Dec 24Dec 30Jan 2Jan 7Jan 13Jan 18Jan 31

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°F218210205201198192187182174
32°F243235229224220216211206198
28°F270261254249244239234229220
24°F302292285276270263259252244
20°F335323314307302295288281270
16°F365354345337331323314306297

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
99% of years
16°F or colder
89% 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
3,120
Cooling degree days, base 65°F
1,711
Growing degree days, base 40°F
7,933
Growing degree days, base 45°F
6,372
Growing degree days, base 50°F
4,964
Growing degree days, base 55°F
3,713
Growing degree days, base 60°F
2,629

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January724031
February557151
March40511160
April15954356
May43163585
June4336783
July0445910
August0408873
September15232667
October15153376
November4135128
December649145

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 8.3 km from Trinity. 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 USC00314063 (High Pt). Public domain.