Johnson City climate

Johnson City Frost Dates and Growing Season

NOAA 1991-2020 normals for Johnson City 2N, 2.6 km from Johnson City, elevation 1137 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Johnson City 2N. 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 22 and the first fall freeze around November 9, a growing season of about 235 days.

Median at 36°F
last April 4, first November 1
Median at 32°F
last March 22, first November 9
Median at 28°F
last March 6, first November 22

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 24Apr 18Apr 13Apr 8Apr 4Mar 31Mar 28Mar 23Mar 14
32°FApr 11Apr 4Mar 31Mar 27Mar 22Mar 16Mar 11Mar 5Feb 27
28°FMar 28Mar 20Mar 15Mar 10Mar 6Mar 2Feb 27Feb 22Feb 11
24°FMar 15Mar 8Mar 3Feb 27Feb 22Feb 12Feb 5Jan 29Jan 19
20°FMar 5Feb 24Feb 11Feb 3Jan 29Jan 23Jan 15Jan 5Dec 26
16°FFeb 18Feb 4Jan 29Jan 22Jan 15Jan 9Jan 4Dec 28Dec 16

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 17Oct 21Oct 25Oct 29Nov 1Nov 2Nov 5Nov 10Nov 16
32°FOct 25Oct 31Nov 2Nov 5Nov 9Nov 12Nov 17Nov 22Nov 30
28°FNov 2Nov 7Nov 12Nov 17Nov 22Nov 27Dec 2Dec 6Dec 15
24°FNov 11Nov 20Nov 26Dec 1Dec 6Dec 10Dec 17Dec 25Jan 3
20°FNov 26Dec 3Dec 9Dec 16Dec 23Dec 29Jan 3Jan 11Jan 26
16°FDec 6Dec 14Dec 23Dec 30Jan 3Jan 6Jan 13Jan 20Feb 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°F235226220215210206200194186
32°F261252245240235229224216207
28°F290280272266260255248241231
24°F333319307300293286277269258
20°F365354344336330321312300287
16°F365365365365364354346337325

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
99% of years
20°F or colder
89% of years
16°F or colder
52% 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
1,940
Cooling degree days, base 65°F
2,689
Growing degree days, base 40°F
9,937
Growing degree days, base 45°F
8,221
Growing degree days, base 50°F
6,614
Growing degree days, base 55°F
5,144
Growing degree days, base 60°F
3,832

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January509496
February36710142
March20645330
April75120497
May10306761
June0474924
July05721,037
August05801,045
September4372818
October66162564
November24738277
December4567124

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 2.6 km from Johnson City. 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 USC00414605 (Johnson City 2N). Public domain.