Weld County climate

Weld County Frost Dates and Growing Season

NOAA 1991-2020 normals for Briggsdale, 10.3 km from Weld County, elevation 4862 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Briggsdale. 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 12 and the first fall freeze around September 28, a growing season of about 135 days.

Median at 36°F
last May 23, first September 19
Median at 32°F
last May 12, first September 28
Median at 28°F
last May 3, first October 5

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 6Jun 2May 29May 26May 23May 21May 18May 16May 12
32°FMay 25May 21May 18May 15May 12May 10May 8May 5May 2
28°FMay 16May 11May 8May 5May 3May 1Apr 29Apr 26Apr 22
24°FMay 7May 2Apr 30Apr 27Apr 24Apr 20Apr 17Apr 14Apr 9
20°FApr 30Apr 24Apr 20Apr 16Apr 13Apr 10Apr 6Apr 3Mar 29
16°FApr 20Apr 14Apr 9Apr 5Apr 2Mar 31Mar 27Mar 22Mar 16

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 6Sep 11Sep 14Sep 17Sep 19Sep 21Sep 24Sep 26Sep 29
32°FSep 15Sep 20Sep 23Sep 25Sep 28Sep 29Oct 1Oct 4Oct 7
28°FSep 23Sep 27Sep 30Oct 3Oct 5Oct 7Oct 10Oct 13Oct 17
24°FSep 30Oct 5Oct 8Oct 11Oct 14Oct 16Oct 19Oct 22Oct 25
20°FOct 10Oct 14Oct 18Oct 20Oct 23Oct 25Oct 27Oct 30Nov 3
16°FOct 17Oct 22Oct 25Oct 28Oct 31Nov 2Nov 5Nov 8Nov 13

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°F13212712312011711210910497
32°F151145141138135131128123117
28°F171164160156153150146141134
24°F189183179175171168164160154
20°F209203199195191186182176169
16°F231224219214210206201196188

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
6,855
Cooling degree days, base 65°F
600
Growing degree days, base 40°F
4,571
Growing degree days, base 45°F
3,491
Growing degree days, base 50°F
2,561
Growing degree days, base 55°F
1,774
Growing degree days, base 60°F
1,119

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,22300
February1,02300
March83407
April573046
May29011222
June60112504
July5256716
August15182632
September15238348
October529082
November91505
December1,23700

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 10.3 km from Weld County. 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 USC00050945 (Briggsdale). Public domain.