Altoona climate

Altoona Frost Dates and Growing Season

NOAA 1991-2020 normals for Eau Claire 3SW, 6.1 km from Altoona, elevation 880 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Eau Claire 3SW. 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 April 24 and the first fall freeze around October 14, a growing season of about 170 days.

Median at 36°F
last May 5, first October 3
Median at 32°F
last April 24, first October 14
Median at 28°F
last April 14, first October 26

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 17May 12May 9May 7May 5May 2Apr 30Apr 25Apr 20
32°FMay 7May 2Apr 30Apr 27Apr 24Apr 21Apr 18Apr 15Apr 9
28°FApr 30Apr 24Apr 20Apr 17Apr 14Apr 11Apr 8Apr 4Apr 1
24°FApr 20Apr 15Apr 10Apr 8Apr 5Apr 3Apr 1Mar 28Mar 22
20°FApr 11Apr 6Apr 3Apr 1Mar 30Mar 27Mar 23Mar 19Mar 14
16°FApr 4Mar 31Mar 28Mar 24Mar 21Mar 18Mar 15Mar 11Mar 6

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 19Sep 23Sep 27Sep 30Oct 3Oct 6Oct 9Oct 12Oct 17
32°FSep 26Oct 1Oct 7Oct 11Oct 14Oct 17Oct 20Oct 23Oct 28
28°FOct 10Oct 17Oct 21Oct 23Oct 26Oct 29Oct 31Nov 2Nov 7
24°FOct 22Oct 27Oct 30Nov 1Nov 3Nov 6Nov 9Nov 13Nov 17
20°FNov 1Nov 4Nov 7Nov 10Nov 13Nov 15Nov 18Nov 23Nov 28
16°FNov 7Nov 11Nov 14Nov 17Nov 20Nov 23Nov 26Nov 30Dec 4

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°F167161157153150147142137130
32°F192185180175170167161156149
28°F212205200196192188184179171
24°F229222218214210206202197189
20°F248241236231227223220215209
16°F263255250246243238233229221

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
7,515
Cooling degree days, base 65°F
637
Growing degree days, base 40°F
4,696
Growing degree days, base 45°F
3,651
Growing degree days, base 50°F
2,719
Growing degree days, base 55°F
1,903
Growing degree days, base 60°F
1,206

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,51200
February1,25400
March1,000117
April568373
May22234296
June34124540
July6229688
August16184634
September15759361
October5013100
November920011
December1,32500

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 6.1 km from Altoona. 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 USC00472425 (Eau Claire 3SW). Public domain.