Sawmill climate

Sawmill Frost Dates and Growing Season

NOAA 1991-2020 normals for Window Rock AP, 28.9 km from Sawmill, elevation 6739 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Window Rock AP. 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 29 and the first fall freeze around September 28, a growing season of about 121 days.

Median at 36°F
last June 8, first September 20
Median at 32°F
last May 29, first September 28
Median at 28°F
last May 13, first October 4

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 13Jun 10Jun 8Jun 6Jun 3Jun 1May 28
32°FJun 10Jun 6Jun 2May 31May 29May 25May 22May 17May 12
28°FJun 1May 26May 20May 17May 13May 10May 7May 4Apr 30
24°FMay 17May 11May 7May 4May 2Apr 29Apr 25Apr 21Apr 17
20°FMay 7May 2Apr 27Apr 22Apr 19Apr 15Apr 12Apr 8Apr 3
16°FApr 26Apr 18Apr 12Apr 6Apr 1Mar 27Mar 19Mar 13Mar 6

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 9Sep 13Sep 16Sep 18Sep 20Sep 23Sep 25Sep 27Oct 1
32°FSep 16Sep 20Sep 23Sep 25Sep 28Sep 30Oct 1Oct 4Oct 8
28°FSep 23Sep 28Oct 1Oct 2Oct 4Oct 7Oct 10Oct 14Oct 20
24°FOct 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 21Oct 25Oct 30
20°FOct 9Oct 14Oct 17Oct 21Oct 25Oct 28Nov 1Nov 4Nov 8
16°FOct 17Oct 24Oct 29Nov 2Nov 4Nov 7Nov 11Nov 15Nov 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°F11811310810510299969288
32°F140134129125121118114109104
28°F163155150147143139134129122
24°F185178172168164159155149143
20°F210203197192187183177171164
16°F248237230223216209204196188

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
6,158
Cooling degree days, base 65°F
414
Growing degree days, base 40°F
4,412
Growing degree days, base 45°F
3,271
Growing degree days, base 50°F
2,321
Growing degree days, base 55°F
1,536
Growing degree days, base 60°F
900

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,09000
February86200
March75503
April546034
May3094188
June6369457
July1204668
August11120574
September14216328
October490068
November79402
December1,09400

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 28.9 km from Sawmill. 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 USW00003029 (Window Rock AP). Public domain.