Florence climate

Florence Frost Dates and Growing Season

NOAA 1991-2020 normals for Stevensville, 13.2 km from Florence, elevation 3375 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Stevensville. 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 22 and the first fall freeze around September 19, a growing season of about 115 days.

Median at 32°F
last May 22, first September 19
Median at 28°F
last May 5, first October 1

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°FJun 13Jun 4May 30May 26May 22May 18May 14May 11May 7
28°FMay 19May 14May 11May 8May 5May 3May 1Apr 28Apr 23
24°FMay 8May 3Apr 30Apr 27Apr 24Apr 21Apr 18Apr 13Apr 8
20°FApr 27Apr 19Apr 13Apr 9Apr 5Apr 1Mar 28Mar 23Mar 14
16°FApr 2Mar 28Mar 21Mar 16Mar 13Mar 9Mar 4Mar 1Feb 23

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°FSep 3Sep 8Sep 13Sep 16Sep 19Sep 22Sep 24Sep 28Oct 2
28°FSep 15Sep 22Sep 25Sep 28Oct 1Oct 3Oct 6Oct 10Oct 15
24°FSep 26Oct 1Oct 5Oct 8Oct 12Oct 17Oct 20Oct 25Oct 30
20°FOct 7Oct 13Oct 19Oct 23Oct 27Oct 30Nov 1Nov 5Nov 11
16°FOct 19Oct 26Nov 1Nov 4Nov 7Nov 11Nov 15Nov 20Nov 25

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°F1029489837772655849
32°F1391321251201151101059887
28°F166159154150147142139134126
24°F194186180175170165160155147
20°F228220213208203197191185174
16°F263253247241236231225217206

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
7,270
Cooling degree days, base 65°F
217
Growing degree days, base 40°F
3,636
Growing degree days, base 45°F
2,608
Growing degree days, base 50°F
1,760
Growing degree days, base 55°F
1,076
Growing degree days, base 60°F
558

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18600
February98700
March83903
April600027
May3693141
June17124306
July42109532
August5874482
September2488228
October619038
November94502
December1,20900

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 13.2 km from Florence. 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 USC00247894 (Stevensville). Public domain.