Orofino climate

Orofino Frost Dates and Growing Season

NOAA 1991-2020 normals for Dworshak Fish Hatchery, 5.7 km from Orofino, elevation 995 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dworshak Fish Hatchery. 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 20 and the first fall freeze around October 20, a growing season of about 182 days.

Median at 36°F
last May 5, first October 6
Median at 32°F
last April 20, first October 20
Median at 28°F
last March 28, first November 2

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 19May 14May 10May 8May 5May 3May 1Apr 29Apr 23
32°FMay 5May 1Apr 27Apr 24Apr 20Apr 16Apr 12Apr 8Apr 1
28°FApr 18Apr 9Apr 4Mar 31Mar 28Mar 23Mar 18Mar 14Mar 7
24°FMar 26Mar 16Mar 12Mar 8Mar 4Mar 1Feb 25Feb 19Feb 10
20°FMar 8Mar 3Feb 27Feb 21Feb 16Feb 10Feb 1Jan 22Jan 9
16°FMar 1Feb 23Feb 16Feb 9Feb 2Jan 24Jan 15Jan 7Dec 24

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 20Sep 26Oct 1Oct 4Oct 6Oct 10Oct 13Oct 17Oct 24
32°FSep 30Oct 7Oct 12Oct 17Oct 20Oct 24Oct 28Nov 1Nov 7
28°FOct 14Oct 22Oct 27Oct 31Nov 2Nov 7Nov 12Nov 17Nov 23
24°FOct 25Nov 1Nov 9Nov 14Nov 19Nov 23Nov 28Dec 3Dec 11
20°FNov 7Nov 15Nov 23Nov 28Dec 3Dec 9Dec 15Dec 25Jan 4
16°FNov 21Nov 30Dec 7Dec 12Dec 20Dec 28Jan 3Jan 13Jan 31

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°F173167162157153150145139131
32°F207199192187182178173167158
28°F249239231225219214209202190
24°F295282275269261254247238227
20°F333319311304296287279271257
16°F364352341333325317309300287

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
99% of years
16°F or colder
88% 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
5,459
Cooling degree days, base 65°F
625
Growing degree days, base 40°F
4,908
Growing degree days, base 45°F
3,687
Growing degree days, base 50°F
2,671
Growing degree days, base 55°F
1,832
Growing degree days, base 60°F
1,149

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January96600
February77100
March659012
April444178
May23021267
June9170430
July11234688
August13230682
September10769414
October437198
November75003
December98300

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 5.7 km from Orofino. 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 USC00102845 (Dworshak Fish Hatchery). Public domain.