Jena climate

Jena Frost Dates and Growing Season

NOAA 1991-2020 normals for Jena, 0.7 km from Jena, elevation 143 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jena. 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 March 19 and the first fall freeze around November 12, a growing season of about 238 days.

Median at 36°F
last April 2, first November 1
Median at 32°F
last March 19, first November 12
Median at 28°F
last March 1, first November 25

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°FApr 21Apr 15Apr 10Apr 6Apr 2Mar 30Mar 25Mar 19Mar 12
32°FApr 9Apr 4Mar 30Mar 25Mar 19Mar 14Mar 8Mar 2Feb 25
28°FMar 29Mar 19Mar 12Mar 6Mar 1Feb 25Feb 19Feb 11Jan 31
24°FMar 11Mar 4Feb 25Feb 17Feb 9Feb 1Jan 28Jan 19Jan 7
20°FMar 1Feb 17Feb 4Jan 30Jan 25Jan 18Jan 12Jan 5Dec 28
16°FFeb 12Feb 2Jan 30Jan 25Jan 18Jan 12Jan 8Jan 3Dec 28

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°FOct 18Oct 23Oct 26Oct 29Nov 1Nov 4Nov 6Nov 11Nov 16
32°FOct 29Nov 2Nov 5Nov 8Nov 12Nov 15Nov 20Nov 25Dec 2
28°FNov 6Nov 12Nov 17Nov 21Nov 25Nov 30Dec 4Dec 9Dec 23
24°FNov 18Nov 26Dec 1Dec 7Dec 14Dec 23Dec 31Jan 5Jan 15
20°FDec 6Dec 19Dec 26Jan 1Jan 4Jan 8Jan 14Jan 21Feb 3
16°FDec 25Jan 1Jan 2Jan 5Jan 9Jan 13Jan 19Jan 27Feb 3

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°F238230223217212208203197189
32°F268258251244238232226219211
28°F303291282273267260255247236
24°F347334326314306299292283270
20°F365365364353344336328314303
16°F365365365365365365362352334

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
97% of years
20°F or colder
70% of years
16°F or colder
31% 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
2,275
Cooling degree days, base 65°F
2,297
Growing degree days, base 40°F
9,247
Growing degree days, base 45°F
7,577
Growing degree days, base 50°F
6,033
Growing degree days, base 55°F
4,628
Growing degree days, base 60°F
3,376

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January572383
February4108121
March25433283
April10687436
May16244693
June0414864
July0511976
August0504969
September5347792
October94119494
November30720215
December5117108

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 0.7 km from Jena. 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 USC00164696 (Jena). Public domain.