Lyman climate

Lyman Frost Dates and Growing Season

NOAA 1991-2020 normals for Mtn View, 7.8 km from Lyman, elevation 6800 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mtn View. 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 14 and the first fall freeze around September 9, a growing season of about 84 days.

Median at 32°F
last June 14, first September 9
Median at 28°F
last May 30, first September 20

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°F–––––––––
32°FJul 1Jun 26Jun 21Jun 17Jun 14Jun 11Jun 8Jun 4May 31
28°FJun 17Jun 10Jun 5Jun 2May 30May 27May 23May 19May 15
24°FJun 1May 26May 21May 17May 14May 10May 7May 3Apr 29
20°FMay 16May 11May 6May 3Apr 30Apr 27Apr 24Apr 20Apr 14
16°FMay 5Apr 30Apr 26Apr 22Apr 18Apr 14Apr 10Apr 6Mar 31

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°F–––––––––
32°FAug 23Aug 30Sep 3Sep 6Sep 9Sep 11Sep 14Sep 18Sep 21
28°FSep 5Sep 10Sep 14Sep 17Sep 20Sep 23Sep 25Sep 28Oct 1
24°FSep 16Sep 21Sep 24Sep 27Sep 30Oct 2Oct 5Oct 9Oct 16
20°FSep 26Sep 30Oct 4Oct 8Oct 12Oct 16Oct 19Oct 24Oct 29
16°FOct 6Oct 13Oct 18Oct 22Oct 25Oct 28Oct 31Nov 3Nov 7

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°F807369646055504336
32°F1049893888480756959
28°F1311241181141091061029688
24°F160152146141137133128122114
20°F187178172167162157153147139
16°F213204199193189183178172164

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
8,848
Cooling degree days, base 65°F
45
Growing degree days, base 40°F
2,809
Growing degree days, base 45°F
1,939
Growing degree days, base 50°F
1,223
Growing degree days, base 55°F
651
Growing degree days, base 60°F
246

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,35000
February1,19300
March1,03400
April78906
May537063
June2654211
July8226410
August11814363
September3431151
October701021
November1,07300
December1,36500

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 7.8 km from Lyman. 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 USC00486555 (Mtn View). Public domain.