Juniata County climate

Juniata County Frost Dates and Growing Season

NOAA 1991-2020 normals for Lewistown, 15.4 km from Juniata County, elevation 460 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lewistown. 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 21 and the first fall freeze around October 24, a growing season of about 185 days.

Median at 36°F
last May 2, first October 13
Median at 32°F
last April 21, first October 24
Median at 28°F
last April 6, first November 5

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 19May 14May 9May 6May 2Apr 30Apr 27Apr 23Apr 18
32°FMay 9May 1Apr 28Apr 24Apr 21Apr 18Apr 15Apr 11Apr 6
28°FApr 21Apr 16Apr 12Apr 9Apr 6Apr 4Apr 1Mar 30Mar 24
24°FApr 8Apr 3Mar 31Mar 29Mar 26Mar 22Mar 19Mar 16Mar 9
20°FMar 26Mar 21Mar 18Mar 16Mar 13Mar 9Mar 6Mar 2Feb 25
16°FMar 20Mar 14Mar 10Mar 6Mar 3Feb 28Feb 24Feb 18Feb 10

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 29Oct 1Oct 5Oct 9Oct 13Oct 16Oct 19Oct 22Oct 27
32°FOct 7Oct 13Oct 17Oct 21Oct 24Oct 27Oct 31Nov 2Nov 7
28°FOct 21Oct 27Nov 1Nov 2Nov 5Nov 8Nov 11Nov 14Nov 19
24°FNov 4Nov 9Nov 12Nov 15Nov 18Nov 21Nov 25Nov 29Dec 4
20°FNov 15Nov 21Nov 27Dec 1Dec 2Dec 6Dec 10Dec 17Dec 23
16°FNov 30Dec 5Dec 11Dec 16Dec 21Dec 25Dec 29Jan 1Jan 9

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°F181173169165161156151146137
32°F206199195190185182177171162
28°F231224219215211208203198190
24°F259252246242238234229225219
20°F290281274269264260254249242
16°F316305299295291285280273264

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
5,570
Cooling degree days, base 65°F
832
Growing degree days, base 40°F
5,428
Growing degree days, base 45°F
4,223
Growing degree days, base 50°F
3,165
Growing degree days, base 55°F
2,247
Growing degree days, base 60°F
1,468

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,11601
February94201
March797021
April4337119
May17549346
June28163585
July2279742
August5233693
September8190460
October36012166
November666027
December96603

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 15.4 km from Juniata County. 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 USC00364992 (Lewistown). Public domain.