Rosalia climate

Rosalia Frost Dates and Growing Season

NOAA 1991-2020 normals for Rosalia, 0.5 km from Rosalia, elevation 2420 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rosalia. 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 7 and the first fall freeze around September 28, a growing season of about 144 days.

Median at 36°F
last May 31, first September 13
Median at 32°F
last May 7, first September 28
Median at 28°F
last April 20, first October 12

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°FJul 5Jun 23Jun 12Jun 5May 31May 27May 22May 16May 8
32°FMay 25May 19May 14May 10May 7May 4May 1Apr 27Apr 22
28°FMay 8May 3Apr 29Apr 25Apr 20Apr 16Apr 10Apr 1Mar 25
24°FApr 20Apr 10Apr 3Mar 29Mar 22Mar 16Mar 12Mar 7Feb 28
20°FMar 29Mar 17Mar 10Mar 5Mar 1Feb 26Feb 20Feb 12Feb 2
16°FMar 11Mar 3Feb 28Feb 22Feb 16Feb 9Feb 3Jan 27Jan 12

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°FAug 26Sep 2Sep 5Sep 10Sep 13Sep 17Sep 21Sep 23Sep 28
32°FSep 11Sep 16Sep 21Sep 25Sep 28Oct 1Oct 4Oct 9Oct 16
28°FSep 25Oct 1Oct 4Oct 7Oct 12Oct 16Oct 20Oct 25Nov 2
24°FOct 6Oct 14Oct 20Oct 24Oct 28Oct 31Nov 3Nov 10Nov 20
20°FOct 21Oct 28Nov 1Nov 5Nov 10Nov 17Nov 23Nov 28Dec 5
16°FOct 31Nov 6Nov 13Nov 21Nov 27Dec 1Dec 7Dec 13Dec 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°F13212411511010397888068
32°F167159153148144139133128117
28°F206195187181175169164157149
24°F249239230223216210202193181
20°F288276267260254246240230219
16°F325312300292283275267258245

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
6,509
Cooling degree days, base 65°F
377
Growing degree days, base 40°F
4,039
Growing degree days, base 45°F
2,940
Growing degree days, base 50°F
2,044
Growing degree days, base 55°F
1,322
Growing degree days, base 60°F
766

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06600
February87101
March77205
April558042
May33410181
June17933310
July49148564
August45147568
September19337304
October531166
November83404
December1,07700

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 0.5 km from Rosalia. 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 USC00457180 (Rosalia). Public domain.