Castro County climate

Castro County Frost Dates and Growing Season

NOAA 1991-2020 normals for Dimmitt 2 N, 7.7 km from Castro County, elevation 3850 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dimmitt 2 N. 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 22 and the first fall freeze around October 23, a growing season of about 182 days.

Median at 36°F
last April 30, first October 14
Median at 32°F
last April 22, first October 23
Median at 28°F
last April 10, first November 1

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 11May 7May 5May 3Apr 30Apr 29Apr 26Apr 22Apr 19
32°FMay 4Apr 30Apr 27Apr 24Apr 22Apr 20Apr 16Apr 12Apr 8
28°FApr 27Apr 21Apr 17Apr 13Apr 10Apr 7Apr 3Mar 31Mar 25
24°FApr 16Apr 9Apr 5Apr 2Mar 30Mar 25Mar 20Mar 16Mar 9
20°FApr 3Mar 30Mar 24Mar 19Mar 14Mar 10Mar 6Mar 3Feb 25
16°FMar 20Mar 13Mar 8Mar 5Mar 2Feb 27Feb 23Feb 17Feb 10

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°FSep 30Oct 4Oct 8Oct 10Oct 14Oct 17Oct 19Oct 22Oct 26
32°FOct 9Oct 14Oct 17Oct 20Oct 23Oct 25Oct 28Nov 1Nov 4
28°FOct 19Oct 24Oct 28Oct 30Nov 1Nov 4Nov 6Nov 9Nov 15
24°FOct 29Nov 1Nov 5Nov 8Nov 10Nov 13Nov 16Nov 20Nov 25
20°FNov 3Nov 9Nov 13Nov 17Nov 20Nov 23Nov 27Dec 1Dec 4
16°FNov 11Nov 18Nov 23Nov 27Nov 30Dec 3Dec 7Dec 11Dec 18

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°F180175171167163160157152146
32°F201195190186182179175171164
28°F224215210206202198194188180
24°F248239234228224219215210203
20°F273264258253248244238232222
16°F302292285279274268262255247

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
4,235
Cooling degree days, base 65°F
1,340
Growing degree days, base 40°F
6,770
Growing degree days, base 45°F
5,356
Growing degree days, base 50°F
4,111
Growing degree days, base 55°F
3,036
Growing degree days, base 60°F
2,114

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January87306
February694017
March536181
April29812210
May100104475
June5299744
July1390854
August2350814
September43160569
October25123273
November580160
December85408

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 7.7 km from Castro County. 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 USC00412464 (Dimmitt 2 N). Public domain.