Ravenna climate

Ravenna Frost Dates and Growing Season

NOAA 1991-2020 normals for Ravenna, 1 km from Ravenna, elevation 2046 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ravenna. 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 3, a growing season of about 150 days.

Median at 36°F
last May 14, first September 27
Median at 32°F
last May 4, first October 3
Median at 28°F
last April 27, first October 12

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 26May 23May 20May 17May 14May 11May 9May 6May 2
32°FMay 18May 12May 9May 6May 4May 2Apr 30Apr 27Apr 23
28°FMay 9May 4May 1Apr 29Apr 27Apr 24Apr 20Apr 16Apr 11
24°FApr 30Apr 27Apr 24Apr 21Apr 18Apr 14Apr 10Apr 7Apr 2
20°FApr 22Apr 18Apr 14Apr 10Apr 7Apr 3Mar 31Mar 28Mar 21
16°FApr 14Apr 8Apr 4Apr 1Mar 29Mar 26Mar 22Mar 17Mar 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 13Sep 18Sep 22Sep 25Sep 27Sep 29Oct 1Oct 4Oct 7
32°FSep 22Sep 26Sep 29Oct 1Oct 3Oct 6Oct 8Oct 12Oct 16
28°FSep 27Oct 2Oct 6Oct 9Oct 12Oct 15Oct 18Oct 21Oct 25
24°FOct 4Oct 12Oct 16Oct 19Oct 22Oct 25Oct 27Oct 31Nov 4
20°FOct 17Oct 21Oct 25Oct 28Oct 31Nov 2Nov 5Nov 8Nov 12
16°FOct 24Oct 30Nov 1Nov 4Nov 7Nov 10Nov 13Nov 17Nov 23

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°F151146142138135131128123118
32°F169162157154150147143139132
28°F190183178174169165161156148
24°F208202196192187183179173166
20°F227220214209206201197191184
16°F249239233228224218214208200

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
6,472
Cooling degree days, base 65°F
898
Growing degree days, base 40°F
5,238
Growing degree days, base 45°F
4,108
Growing degree days, base 50°F
3,111
Growing degree days, base 55°F
2,244
Growing degree days, base 60°F
1,506

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,25700
February1,04702
March828024
April503595
May21648319
June30188608
July4312773
August11243697
September11694434
October4458140
November830017
December1,18600

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 1 km from Ravenna. 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 USC00257040 (Ravenna). Public domain.