Mentone climate

Mentone Frost Dates and Growing Season

NOAA 1991-2020 normals for Rochester, 18.8 km from Mentone, elevation 760 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rochester. 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 April 23 and the first fall freeze around October 21, a growing season of about 180 days.

Median at 36°F
last May 3, first October 10
Median at 32°F
last April 23, first October 21
Median at 28°F
last April 10, first November 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°FMay 20May 15May 11May 7May 3Apr 30Apr 28Apr 24Apr 20
32°FMay 9May 3Apr 29Apr 26Apr 23Apr 20Apr 18Apr 14Apr 9
28°FApr 26Apr 21Apr 17Apr 14Apr 10Apr 7Apr 5Apr 2Mar 28
24°FApr 15Apr 9Apr 5Apr 3Apr 1Mar 30Mar 25Mar 21Mar 15
20°FApr 4Mar 31Mar 27Mar 24Mar 21Mar 17Mar 13Mar 9Mar 3
16°FMar 26Mar 21Mar 16Mar 13Mar 10Mar 6Mar 3Feb 28Feb 21

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 27Oct 1Oct 4Oct 7Oct 10Oct 12Oct 15Oct 18Oct 23
32°FOct 6Oct 12Oct 15Oct 18Oct 21Oct 23Oct 26Oct 29Nov 2
28°FOct 19Oct 24Oct 27Oct 31Nov 1Nov 3Nov 6Nov 10Nov 17
24°FNov 1Nov 3Nov 6Nov 8Nov 12Nov 17Nov 22Nov 26Dec 2
20°FNov 7Nov 11Nov 17Nov 21Nov 25Nov 29Dec 2Dec 7Dec 15
16°FNov 17Nov 24Nov 28Dec 1Dec 5Dec 8Dec 13Dec 18Dec 24

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°F177170166162158154149144137
32°F200194188184180176171165158
28°F226219213209205201197191185
24°F251243238233229224219215207
20°F272265260255250246240234226
16°F294285280274270265260254246

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
6,168
Cooling degree days, base 65°F
814
Growing degree days, base 40°F
5,272
Growing degree days, base 45°F
4,117
Growing degree days, base 50°F
3,097
Growing degree days, base 55°F
2,203
Growing degree days, base 60°F
1,441

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,25201
February1,04302
March848227
April4787109
May19660343
June32183602
July5253713
August11205659
September10291443
October38614167
November734030
December1,08203

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 18.8 km from Mentone. 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 USC00127482 (Rochester). Public domain.