Nederland climate

Nederland Frost Dates and Growing Season

NOAA 1991-2020 normals for Boulder 14 W, 8.6 km from Nederland, elevation 9829 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Boulder 14 W. 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 June 21 and the first fall freeze around September 2, a growing season of about 71 days.

Median at 32°F
last June 21, first September 2
Median at 28°F
last June 4, first September 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°F–––––––––
32°FJul 4Jun 30Jun 27Jun 24Jun 21Jun 18Jun 15Jun 12Jun 7
28°FJun 20Jun 15Jun 10Jun 7Jun 4Jun 1May 30May 26May 22
24°FJun 4May 30May 25May 22May 19May 16May 13May 10May 7
20°FMay 22May 16May 13May 10May 8May 5May 3May 1Apr 26
16°FMay 12May 8May 4May 2Apr 30Apr 27Apr 22Apr 19Apr 14

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°F–––––––––
32°FAug 17Aug 24Aug 28Aug 31Sep 2Sep 4Sep 7Sep 10Sep 15
28°FSep 2Sep 5Sep 8Sep 11Sep 14Sep 17Sep 19Sep 23Sep 27
24°FSep 10Sep 15Sep 19Sep 22Sep 25Sep 27Sep 30Oct 4Oct 9
20°FSep 18Sep 25Sep 29Oct 2Oct 5Oct 10Oct 13Oct 18Oct 23
16°FSep 29Oct 4Oct 9Oct 13Oct 17Oct 20Oct 24Oct 28Nov 2

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°F595248433935312823
32°F908480767167645851
28°F11911310910410096928881
24°F147140135131126122117112105
20°F170164158154150146141135127
16°F191184179174170165160155146

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
10,824
Cooling degree days, base 65°F
0
Growing degree days, base 40°F
1,526
Growing degree days, base 45°F
865
Growing degree days, base 50°F
385
Growing degree days, base 55°F
102
Growing degree days, base 60°F
8

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,38900
February1,27000
March1,20400
April1,02300
May79503
June485056
July3040170
August3630125
September569030
October88702
November1,13400
December1,40300

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 8.6 km from Nederland. 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 USW00094075 (Boulder 14 W). Public domain.