Arvada climate

Arvada Frost Dates and Growing Season

NOAA 1991-2020 normals for Wheat Ridge 2, 4 km from Arvada, elevation 5398 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wheat Ridge 2. 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 5 and the first fall freeze around October 5, a growing season of about 151 days.

Median at 36°F
last May 16, first September 26
Median at 32°F
last May 5, first October 5
Median at 28°F
last April 25, first October 14

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 31May 27May 22May 19May 16May 14May 11May 8May 5
32°FMay 18May 13May 11May 8May 5May 3May 1Apr 28Apr 24
28°FMay 9May 3May 1Apr 28Apr 25Apr 22Apr 19Apr 16Apr 11
24°FApr 29Apr 23Apr 20Apr 17Apr 13Apr 10Apr 6Apr 2Mar 27
20°FApr 20Apr 13Apr 8Apr 5Apr 1Mar 30Mar 25Mar 19Mar 13
16°FApr 10Apr 3Mar 30Mar 25Mar 19Mar 14Mar 9Mar 5Mar 1

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 13Sep 17Sep 20Sep 23Sep 26Sep 29Oct 1Oct 4Oct 7
32°FSep 20Sep 25Sep 29Oct 2Oct 5Oct 7Oct 10Oct 12Oct 18
28°FSep 28Oct 4Oct 8Oct 11Oct 14Oct 17Oct 20Oct 22Oct 26
24°FOct 8Oct 14Oct 18Oct 20Oct 24Oct 26Oct 30Nov 2Nov 7
20°FOct 17Oct 23Oct 27Oct 30Nov 2Nov 5Nov 8Nov 13Nov 18
16°FOct 24Oct 31Nov 4Nov 7Nov 11Nov 15Nov 19Nov 22Nov 26

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°F148142138133131127123118112
32°F167162158154151147143138132
28°F191184178174170167162157149
24°F213208202196192188184179171
20°F238228222218213208202196189
16°F262253246241236230224217207

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
5,926
Cooling degree days, base 65°F
593
Growing degree days, base 40°F
4,886
Growing degree days, base 45°F
3,693
Growing degree days, base 50°F
2,681
Growing degree days, base 55°F
1,834
Growing degree days, base 60°F
1,138

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,01801
February88803
March736023
April527173
May27215245
June56110505
July6238697
August14181632
September13548375
October4721109
November770018
December1,03402

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 4 km from Arvada. 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 USC00058995 (Wheat Ridge 2). Public domain.