Walhalla climate

Walhalla Frost Dates and Growing Season

NOAA 1991-2020 normals for Cavalier 7NW, 17.2 km from Walhalla, elevation 899 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cavalier 7NW. 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 12 and the first fall freeze around September 30, a growing season of about 139 days.

Median at 36°F
last May 22, first September 21
Median at 32°F
last May 12, first September 30
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 3May 31May 28May 25May 22May 19May 16May 13May 9
32°FMay 27May 21May 17May 15May 12May 9May 6May 4Apr 29
28°FMay 17May 12May 8May 5May 2Apr 30Apr 27Apr 22Apr 17
24°FMay 6May 1Apr 29Apr 26Apr 22Apr 19Apr 16Apr 12Apr 6
20°FApr 26Apr 21Apr 18Apr 15Apr 12Apr 9Apr 6Apr 3Mar 30
16°FApr 19Apr 14Apr 10Apr 7Apr 5Apr 3Apr 1Mar 28Mar 21

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 16Sep 18Sep 21Sep 23Sep 26Sep 29Oct 3
32°FSep 17Sep 21Sep 25Sep 28Sep 30Oct 2Oct 5Oct 9Oct 13
28°FSep 27Oct 1Oct 3Oct 6Oct 10Oct 13Oct 16Oct 19Oct 23
24°FOct 4Oct 11Oct 14Oct 18Oct 21Oct 24Oct 27Oct 30Nov 2
20°FOct 15Oct 20Oct 24Oct 27Oct 30Nov 1Nov 3Nov 6Nov 11
16°FOct 24Oct 28Nov 1Nov 2Nov 5Nov 7Nov 10Nov 14Nov 19

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°F139133128125121117114110103
32°F157151147143139136131127121
28°F179172167162158155151146140
24°F201194188183179175170166158
20°F218211207203199195191186179
16°F231225220216212209205200194

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
10,022
Cooling degree days, base 65°F
273
Growing degree days, base 40°F
3,511
Growing degree days, base 45°F
2,630
Growing degree days, base 50°F
1,853
Growing degree days, base 55°F
1,188
Growing degree days, base 60°F
652

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,87700
February1,58200
March1,33201
April783020
May39312165
June11257397
July42106529
August6579479
September27519225
October713137
November1,18701
December1,66200

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 17.2 km from Walhalla. 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 USC00321435 (Cavalier 7NW). Public domain.