Madison County climate

Madison County Frost Dates and Growing Season

NOAA 1991-2020 normals for Virginia City, 2.4 km from Madison County, elevation 5773 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Virginia City. 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 June 4 and the first fall freeze around September 18, a growing season of about 106 days.

Median at 36°F
last June 20, first September 6
Median at 32°F
last June 4, first September 18
Median at 28°F
last May 14, first October 1

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°FJul 6Jul 1Jun 27Jun 23Jun 20Jun 17Jun 14Jun 10Jun 5
32°FJun 23Jun 16Jun 11Jun 8Jun 4May 31May 28May 24May 17
28°FJun 3May 26May 22May 18May 14May 11May 8May 5May 1
24°FMay 16May 10May 7May 5May 1Apr 29Apr 26Apr 22Apr 17
20°FMay 4Apr 29Apr 25Apr 22Apr 18Apr 16Apr 12Apr 8Apr 3
16°FApr 22Apr 17Apr 13Apr 8Apr 4Apr 1Mar 29Mar 23Mar 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°FAug 23Aug 29Sep 1Sep 4Sep 6Sep 9Sep 12Sep 15Sep 20
32°FSep 3Sep 7Sep 12Sep 15Sep 18Sep 20Sep 24Sep 27Oct 2
28°FSep 13Sep 19Sep 23Sep 28Oct 1Oct 3Oct 6Oct 9Oct 14
24°FSep 25Oct 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 21Oct 27
20°FOct 6Oct 11Oct 15Oct 18Oct 22Oct 25Oct 28Nov 1Nov 6
16°FOct 15Oct 20Oct 25Oct 28Nov 1Nov 3Nov 6Nov 11Nov 16

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°F989186827773686254
32°F128121116110106102969183
28°F158151146141137133128121112
24°F182174169165160157153149141
20°F206198193188184180175169161
16°F234224217212208203198193185

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
7,856
Cooling degree days, base 65°F
183
Growing degree days, base 40°F
3,339
Growing degree days, base 45°F
2,384
Growing degree days, base 50°F
1,599
Growing degree days, base 55°F
972
Growing degree days, base 60°F
498

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21100
February1,06000
March94101
April708015
May4541103
June23016250
July5491503
August6967465
September2698218
October636042
November97403
December1,25200

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 2.4 km from Madison 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 USC00248597 (Virginia City). Public domain.