Johnstown climate

Johnstown Frost Dates and Growing Season

NOAA 1991-2020 normals for Loveland 2N, 18.3 km from Johnstown, elevation 5080 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Loveland 2N. 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 10 and the first fall freeze around October 1, a growing season of about 142 days.

Median at 36°F
last May 22, first September 22
Median at 32°F
last May 10, first October 1
Median at 28°F
last May 2, first October 10

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 4May 31May 28May 25May 22May 19May 17May 14May 11
32°FMay 22May 18May 15May 13May 10May 8May 6May 3Apr 30
28°FMay 14May 10May 7May 4May 2Apr 30Apr 27Apr 23Apr 17
24°FMay 6May 1Apr 27Apr 24Apr 20Apr 16Apr 13Apr 9Apr 5
20°FApr 28Apr 22Apr 16Apr 11Apr 8Apr 4Apr 2Mar 30Mar 24
16°FApr 18Apr 8Apr 4Apr 1Mar 29Mar 25Mar 21Mar 16Mar 10

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 8Sep 13Sep 17Sep 20Sep 22Sep 25Sep 28Oct 1Oct 4
32°FSep 15Sep 21Sep 25Sep 28Oct 1Oct 4Oct 7Oct 10Oct 13
28°FSep 22Sep 29Oct 3Oct 7Oct 10Oct 12Oct 15Oct 18Oct 22
24°FOct 4Oct 10Oct 14Oct 17Oct 20Oct 22Oct 25Oct 29Nov 2
20°FOct 13Oct 19Oct 22Oct 26Oct 29Nov 1Nov 3Nov 7Nov 11
16°FOct 21Oct 26Oct 31Nov 3Nov 5Nov 9Nov 12Nov 16Nov 20

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°F140134129125122118115110104
32°F157152148145142138135130124
28°F178172167163159155151146140
24°F200193188184180175170165158
20°F223215210204200195190184176
16°F246237230224220215209204195

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
6,456
Cooling degree days, base 65°F
530
Growing degree days, base 40°F
4,592
Growing degree days, base 45°F
3,470
Growing degree days, base 50°F
2,510
Growing degree days, base 55°F
1,707
Growing degree days, base 60°F
1,047

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,13500
February95801
March789014
April555056
May3079211
June6493479
July7219677
August17166614
September14643358
October506191
November84208
December1,13101

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 18.3 km from Johnstown. 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 USC00055236 (Loveland 2N). Public domain.