Round Rock climate

Round Rock Frost Dates and Growing Season

NOAA 1991-2020 normals for Lukachukai, 24.4 km from Round Rock, elevation 6520 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lukachukai. 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 May 3 and the first fall freeze around October 17, a growing season of about 163 days.

Median at 36°F
last May 16, first October 8
Median at 32°F
last May 3, first October 17
Median at 28°F
last April 23, first October 27

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°FJun 6May 29May 24May 20May 16May 13May 9May 5Apr 30
32°FMay 22May 14May 10May 7May 3Apr 30Apr 28Apr 25Apr 21
28°FMay 9May 3Apr 30Apr 27Apr 23Apr 20Apr 17Apr 13Apr 8
24°FApr 28Apr 21Apr 15Apr 12Apr 9Apr 6Apr 2Mar 29Mar 16
20°FApr 8Apr 1Mar 25Mar 18Mar 13Mar 8Mar 4Feb 28Feb 21
16°FMar 20Mar 11Mar 6Mar 2Feb 27Feb 22Feb 17Feb 12Feb 5

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 24Sep 29Oct 3Oct 5Oct 8Oct 10Oct 13Oct 16Oct 20
32°FOct 2Oct 7Oct 11Oct 14Oct 17Oct 20Oct 23Oct 26Oct 30
28°FOct 11Oct 16Oct 20Oct 23Oct 27Oct 30Nov 2Nov 6Nov 12
24°FOct 20Oct 26Oct 30Nov 2Nov 5Nov 8Nov 12Nov 16Nov 20
20°FOct 27Nov 2Nov 7Nov 12Nov 16Nov 19Nov 21Nov 25Nov 30
16°FNov 5Nov 14Nov 19Nov 22Nov 25Nov 28Dec 1Dec 5Dec 11

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°F165157152148144139134128120
32°F185178172168163159155151143
28°F207199192188183178174169161
24°F234225218213208203198191182
20°F269260255249243236231222212
16°F297288281275270265259252244

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
5,733
Cooling degree days, base 65°F
685
Growing degree days, base 40°F
5,103
Growing degree days, base 45°F
3,910
Growing degree days, base 50°F
2,881
Growing degree days, base 55°F
2,014
Growing degree days, base 60°F
1,280

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12800
February83700
March693012
April526061
May24312256
June36137551
July2255717
August4201662
September6880465
October3871143
November732014
December1,07600

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 24.4 km from Round Rock. 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 USC00025129 (Lukachukai). Public domain.