Dysart climate

Dysart Frost Dates and Growing Season

NOAA 1991-2020 normals for Vinton, 24.6 km from Dysart, elevation 850 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Vinton. 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 3 and the first fall freeze around October 3, a growing season of about 151 days.

Median at 36°F
last May 14, first September 26
Median at 32°F
last May 3, first October 3
Median at 28°F
last April 25, 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°FMay 28May 23May 20May 16May 14May 11May 8May 5Apr 30
32°FMay 17May 12May 9May 6May 3May 1Apr 29Apr 26Apr 21
28°FMay 8May 4Apr 30Apr 27Apr 25Apr 21Apr 18Apr 15Apr 10
24°FApr 29Apr 25Apr 20Apr 17Apr 13Apr 10Apr 7Apr 4Mar 31
20°FApr 21Apr 14Apr 9Apr 6Apr 4Apr 1Mar 29Mar 25Mar 17
16°FApr 9Apr 3Mar 31Mar 28Mar 25Mar 21Mar 17Mar 13Mar 7

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 17Sep 20Sep 23Sep 26Sep 28Oct 1Oct 3Oct 6
32°FSep 20Sep 25Sep 28Oct 1Oct 3Oct 6Oct 8Oct 11Oct 15
28°FSep 29Oct 3Oct 7Oct 10Oct 12Oct 15Oct 18Oct 21Oct 24
24°FOct 8Oct 13Oct 17Oct 20Oct 22Oct 25Oct 27Oct 30Nov 3
20°FOct 17Oct 23Oct 26Oct 29Oct 31Nov 2Nov 5Nov 8Nov 14
16°FOct 29Nov 1Nov 4Nov 7Nov 9Nov 12Nov 16Nov 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°F152146141137134130126121115
32°F169164159155151148144139132
28°F189181177172169165160157151
24°F209203199194190186181176169
20°F231222218214210206201196189
16°F253245240235231226221217210

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
7,441
Cooling degree days, base 65°F
540
Growing degree days, base 40°F
4,564
Growing degree days, base 45°F
3,516
Growing degree days, base 50°F
2,581
Growing degree days, base 55°F
1,766
Growing degree days, base 60°F
1,079

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,49300
February1,22200
March958017
April549378
May24932273
June46120524
July11191645
August28137573
September15853355
October5084105
November909011
December1,31001

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 24.6 km from Dysart. 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 USC00138568 (Vinton). Public domain.