Mono County climate

Mono County Frost Dates and Growing Season

NOAA 1991-2020 normals for Lee Vining, 20.5 km from Mono County, elevation 6797 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lee Vining. 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 23 and the first fall freeze around October 9, a growing season of about 139 days.

Median at 36°F
last June 5, first September 28
Median at 32°F
last May 23, first October 9
Median at 28°F
last May 2, first October 21

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 19Jun 15Jun 11Jun 7Jun 5Jun 3May 31May 27May 20
32°FJun 9Jun 3May 31May 27May 23May 18May 14May 8May 2
28°FMay 26May 17May 11May 6May 2Apr 29Apr 27Apr 23Apr 18
24°FMay 6Apr 30Apr 26Apr 22Apr 19Apr 15Apr 11Apr 7Apr 1
20°FApr 21Apr 14Apr 10Apr 6Apr 2Mar 30Mar 23Mar 15Mar 7
16°FApr 5Mar 29Mar 20Mar 14Mar 8Mar 4Feb 28Feb 22Feb 13

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 15Sep 20Sep 23Sep 26Sep 28Oct 1Oct 3Oct 6Oct 12
32°FSep 27Oct 1Oct 4Oct 6Oct 9Oct 13Oct 16Oct 19Oct 24
28°FOct 5Oct 10Oct 14Oct 17Oct 21Oct 24Oct 28Nov 1Nov 6
24°FOct 15Oct 22Oct 26Oct 31Nov 2Nov 5Nov 8Nov 13Nov 17
20°FOct 29Nov 4Nov 8Nov 11Nov 15Nov 19Nov 23Nov 27Dec 1
16°FNov 10Nov 17Nov 22Nov 27Dec 1Dec 4Dec 7Dec 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°F13412712311811411110810295
32°F163154148143139134129124116
28°F192185179174168163158152143
24°F220213207201195191186180172
20°F255245237232226220214208198
16°F296285277270263256250243231

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
6,236
Cooling degree days, base 65°F
299
Growing degree days, base 40°F
4,201
Growing degree days, base 45°F
3,073
Growing degree days, base 50°F
2,133
Growing degree days, base 55°F
1,364
Growing degree days, base 60°F
751

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06200
February88500
March79706
April594037
May3783152
June13140367
July14138589
August20102547
September14417330
October450096
November74008
December1,02300

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 20.5 km from Mono 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 USC00044881 (Lee Vining). Public domain.