Kellyville climate

Kellyville Frost Dates and Growing Season

NOAA 1991-2020 normals for Bristow, 20.5 km from Kellyville, elevation 830 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bristow. 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 9 and the first fall freeze around October 25, a growing season of about 196 days.

Median at 36°F
last April 22, first October 15
Median at 32°F
last April 9, first October 25
Median at 28°F
last March 28, first November 2

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 6May 1Apr 29Apr 26Apr 22Apr 19Apr 15Apr 12Apr 6
32°FApr 27Apr 22Apr 17Apr 13Apr 9Apr 6Apr 3Mar 31Mar 24
28°FApr 16Apr 9Apr 5Apr 1Mar 28Mar 24Mar 20Mar 15Mar 9
24°FApr 3Mar 27Mar 22Mar 18Mar 14Mar 11Mar 7Mar 3Feb 26
20°FMar 19Mar 14Mar 10Mar 6Mar 3Feb 28Feb 25Feb 20Feb 12
16°FMar 11Mar 6Mar 2Feb 27Feb 23Feb 18Feb 12Feb 5Jan 28

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 1Oct 5Oct 9Oct 13Oct 15Oct 18Oct 21Oct 24Oct 30
32°FOct 10Oct 16Oct 20Oct 23Oct 25Oct 28Oct 31Nov 3Nov 8
28°FOct 20Oct 24Oct 28Oct 31Nov 2Nov 6Nov 9Nov 13Nov 18
24°FOct 28Nov 2Nov 6Nov 9Nov 13Nov 16Nov 21Nov 26Dec 2
20°FNov 5Nov 12Nov 16Nov 21Nov 25Nov 30Dec 3Dec 6Dec 13
16°FNov 16Nov 25Nov 30Dec 3Dec 7Dec 12Dec 18Dec 24Jan 5

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°F196189184179175171166161153
32°F216209204200196191187181174
28°F242235229224218214209202194
24°F268259253247242238232225216
20°F293283276271266260255249240
16°F320309302297290283278270259

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
3,665
Cooling degree days, base 65°F
1,701
Growing degree days, base 40°F
7,590
Growing degree days, base 45°F
6,114
Growing degree days, base 50°F
4,784
Growing degree days, base 55°F
3,601
Growing degree days, base 60°F
2,572

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January846017
February639141
March43611151
April20441305
May58134542
June3325772
July0480945
August1433897
September29223645
October19546334
November4755110
December780025

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 20.5 km from Kellyville. 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 USC00341144 (Bristow). Public domain.