Roxborough Park climate

Roxborough Park Frost Dates and Growing Season

NOAA 1991-2020 normals for Kassler, 2 km from Roxborough Park, elevation 5587 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Kassler. 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 8 and the first fall freeze around October 3, a growing season of about 147 days.

Median at 36°F
last May 19, first September 27
Median at 32°F
last May 8, first October 3
Median at 28°F
last April 29, first October 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°FJun 2May 28May 25May 21May 19May 17May 14May 10May 5
32°FMay 22May 18May 15May 11May 8May 5May 2Apr 30Apr 27
28°FMay 13May 7May 3May 1Apr 29Apr 27Apr 23Apr 20Apr 15
24°FMay 1Apr 27Apr 23Apr 20Apr 17Apr 13Apr 8Apr 4Mar 31
20°FApr 21Apr 15Apr 10Apr 6Apr 3Mar 31Mar 28Mar 23Mar 16
16°FApr 15Apr 8Apr 4Mar 31Mar 27Mar 22Mar 17Mar 11Mar 5

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 19Sep 22Sep 24Sep 27Sep 29Oct 1Oct 3Oct 8
32°FSep 21Sep 26Sep 29Oct 1Oct 3Oct 6Oct 9Oct 13Oct 17
28°FSep 28Oct 3Oct 7Oct 10Oct 13Oct 16Oct 19Oct 22Oct 28
24°FOct 7Oct 13Oct 17Oct 20Oct 23Oct 27Oct 30Nov 1Nov 7
20°FOct 17Oct 23Oct 27Oct 31Nov 2Nov 4Nov 7Nov 11Nov 16
16°FOct 25Oct 31Nov 2Nov 5Nov 9Nov 12Nov 16Nov 20Nov 23

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°F146141137132128124121117110
32°F165159155152147144140135126
28°F187181176172167163159154146
24°F212204199194190185181176168
20°F232223218214209204199194186
16°F251243237231225220215209200

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
6,013
Cooling degree days, base 65°F
645
Growing degree days, base 40°F
4,940
Growing degree days, base 45°F
3,755
Growing degree days, base 50°F
2,743
Growing degree days, base 55°F
1,893
Growing degree days, base 60°F
1,195

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,02602
February90403
March763024
April551169
May29615232
June66112498
July8248705
August16199648
September13166399
October4494133
November758029
December1,04602

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 2 km from Roxborough Park. 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 USC00054452 (Kassler). Public domain.