Marathon climate

Marathon Frost Dates and Growing Season

NOAA 1991-2020 normals for Whitney Pt Dam, 12.4 km from Marathon, elevation 1040 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Whitney Pt Dam. 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 May 4 and the first fall freeze around October 16, a growing season of about 163 days.

Median at 36°F
last May 17, first October 3
Median at 32°F
last May 4, first October 16
Median at 28°F
last April 23, first October 31

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°FJun 1May 27May 24May 20May 17May 14May 10May 7May 2
32°FMay 20May 15May 10May 6May 4May 1Apr 28Apr 26Apr 22
28°FMay 6May 1Apr 29Apr 26Apr 23Apr 20Apr 17Apr 13Apr 8
24°FApr 22Apr 18Apr 15Apr 12Apr 9Apr 6Apr 4Apr 2Mar 31
20°FApr 11Apr 7Apr 5Apr 3Apr 1Mar 31Mar 28Mar 24Mar 18
16°FApr 4Apr 1Mar 31Mar 27Mar 24Mar 20Mar 17Mar 15Mar 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 20Sep 24Sep 28Oct 1Oct 3Oct 5Oct 8Oct 13Oct 19
32°FSep 30Oct 4Oct 8Oct 12Oct 16Oct 20Oct 25Oct 28Nov 2
28°FOct 11Oct 18Oct 24Oct 27Oct 31Nov 2Nov 4Nov 8Nov 13
24°FOct 26Nov 1Nov 5Nov 9Nov 11Nov 14Nov 16Nov 20Nov 27
20°FNov 10Nov 15Nov 17Nov 20Nov 23Nov 27Dec 1Dec 4Dec 8
16°FNov 18Nov 23Nov 27Nov 30Dec 2Dec 5Dec 8Dec 12Dec 19

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°F157152147143138133128124118
32°F185178172167163159154148140
28°F209203199194190185180173165
24°F236229224219215211207203195
20°F256249244240236232228224218
16°F274267261257253249245241234

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
7,000
Cooling degree days, base 65°F
386
Growing degree days, base 40°F
4,275
Growing degree days, base 45°F
3,216
Growing degree days, base 50°F
2,290
Growing degree days, base 55°F
1,500
Growing degree days, base 60°F
857

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27700
February1,14200
March1,02609
April616142
May29715218
June8259428
July15151601
August28115552
September16843329
October469398
November777012
December1,10401

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 12.4 km from Marathon. 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 USC00309442 (Whitney Pt Dam). Public domain.