Byram climate

Byram Frost Dates and Growing Season

NOAA 1991-2020 normals for Westchester CO AP, 8.3 km from Byram, elevation 379 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Westchester CO AP. 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 12 and the first fall freeze around October 31, a growing season of about 200 days.

Median at 36°F
last April 26, first October 18
Median at 32°F
last April 12, first October 31
Median at 28°F
last April 1, first November 13

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 6May 2Apr 30Apr 26Apr 23Apr 20Apr 17Apr 13
32°FApr 27Apr 21Apr 18Apr 15Apr 12Apr 10Apr 7Apr 5Apr 1
28°FApr 13Apr 8Apr 5Apr 3Apr 1Mar 31Mar 28Mar 24Mar 18
24°FApr 3Mar 31Mar 28Mar 25Mar 21Mar 18Mar 15Mar 11Mar 6
20°FMar 27Mar 21Mar 17Mar 14Mar 11Mar 8Mar 5Mar 1Feb 25
16°FMar 17Mar 12Mar 8Mar 5Mar 2Feb 27Feb 24Feb 18Feb 9

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 2Oct 8Oct 11Oct 15Oct 18Oct 22Oct 25Oct 29Nov 2
32°FOct 15Oct 21Oct 24Oct 28Oct 31Nov 2Nov 5Nov 9Nov 14
28°FOct 29Nov 3Nov 6Nov 10Nov 13Nov 16Nov 18Nov 22Nov 29
24°FNov 10Nov 15Nov 18Nov 22Nov 25Nov 28Dec 1Dec 4Dec 10
20°FNov 21Nov 27Nov 30Dec 3Dec 6Dec 10Dec 15Dec 20Dec 25
16°FDec 2Dec 7Dec 13Dec 17Dec 21Dec 25Dec 29Jan 3Jan 10

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°F193187182178174170165160152
32°F219213208204200196192186179
28°F245238233228224220216211204
24°F270262257252247243239234227
20°F293285280275271265261256249
16°F319308302297293288283277269

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
5,492
Cooling degree days, base 65°F
787
Growing degree days, base 40°F
5,382
Growing degree days, base 45°F
4,151
Growing degree days, base 50°F
3,082
Growing degree days, base 55°F
2,165
Growing degree days, base 60°F
1,398

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,09001
February92701
March805015
April465490
May20130300
June35142557
July2282745
August4233694
September7488464
October3418174
November624035
December92505

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 Byram. 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 USW00094745 (Westchester CO AP). Public domain.