Morrison climate

Morrison Frost Dates and Growing Season

NOAA 1991-2020 normals for Mc Minnville, 14.7 km from Morrison, elevation 940 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mc Minnville. 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 7 and the first fall freeze around October 30, a growing season of about 203 days.

Median at 36°F
last April 19, first October 20
Median at 32°F
last April 7, first October 30
Median at 28°F
last March 27, first November 7

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 5Apr 30Apr 26Apr 22Apr 19Apr 16Apr 13Apr 9Apr 4
32°FApr 23Apr 18Apr 14Apr 10Apr 7Apr 4Mar 31Mar 27Mar 20
28°FApr 13Apr 6Apr 2Mar 30Mar 27Mar 22Mar 17Mar 13Mar 5
24°FApr 1Mar 26Mar 21Mar 17Mar 12Mar 6Mar 2Feb 25Feb 18
20°FMar 21Mar 14Mar 8Mar 3Feb 27Feb 22Feb 14Feb 7Jan 30
16°FMar 9Mar 1Feb 24Feb 16Feb 9Feb 3Jan 30Jan 22Jan 12

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°FOct 8Oct 12Oct 15Oct 17Oct 20Oct 23Oct 25Oct 28Nov 1
32°FOct 16Oct 21Oct 24Oct 27Oct 30Nov 1Nov 3Nov 5Nov 10
28°FOct 25Oct 31Nov 2Nov 5Nov 7Nov 10Nov 14Nov 18Nov 25
24°FNov 2Nov 8Nov 12Nov 15Nov 20Nov 24Nov 29Dec 4Dec 9
20°FNov 12Nov 19Nov 27Dec 1Dec 4Dec 9Dec 16Dec 25Jan 3
16°FNov 28Dec 6Dec 12Dec 20Dec 27Jan 1Jan 6Jan 13Jan 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°F202196191187182178174169162
32°F227219213208203199194190182
28°F254244236231227221216210203
24°F280271265259254247241233224
20°F315303294287280275268260250
16°F349336329320313306300290280

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
96% 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
3,286
Cooling degree days, base 65°F
1,565
Growing degree days, base 40°F
7,709
Growing degree days, base 45°F
6,173
Growing degree days, base 50°F
4,782
Growing degree days, base 55°F
3,546
Growing degree days, base 60°F
2,476

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January748140
February580155
March42111158
April18247332
May52143557
June3303750
July0409874
August0378843
September19215646
October17450355
November4446121
December664151

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 14.7 km from Morrison. 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 USC00405882 (Mc Minnville). Public domain.