Markham climate

Markham Frost Dates and Growing Season

NOAA 1991-2020 normals for Bay City Wtr Wks, 9 km from Markham, elevation 52 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bay City Wtr Wks. 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 February 20 and the first fall freeze around December 3, a growing season of about 290 days.

Median at 36°F
last March 7, first November 20
Median at 32°F
last February 20, first December 3
Median at 28°F
last January 31, first December 22

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°FApr 1Mar 23Mar 16Mar 12Mar 7Mar 3Feb 28Feb 22Feb 11
32°FMar 15Mar 8Mar 2Feb 25Feb 20Feb 13Feb 6Jan 30Jan 19
28°FMar 5Feb 23Feb 13Feb 5Jan 31Jan 24Jan 18Jan 8Dec 27
24°FFeb 21Feb 10Jan 31Jan 23Jan 17Jan 9Jan 4Dec 31Dec 16
20°FFeb 9Jan 31Jan 19Jan 11Jan 9Jan 5Jan 2Dec 30Dec 16
16°F–––––––––

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°FNov 3Nov 7Nov 12Nov 16Nov 20Nov 24Nov 29Dec 2Dec 9
32°FNov 10Nov 18Nov 24Nov 29Dec 3Dec 6Dec 13Dec 22Jan 1
28°FNov 24Dec 1Dec 6Dec 13Dec 22Dec 29Jan 4Jan 12Jan 23
24°FDec 8Dec 16Dec 26Jan 1Jan 5Jan 9Jan 16Jan 26Feb 6
20°FDec 15Dec 26Jan 1Jan 4Jan 7Jan 10Jan 16Jan 23Feb 4
16°F–––––––––

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°F290278270264258253246238229
32°F327312303296290282274266255
28°F365352343335329321312302287
24°F365365365365365357348337326
20°F365365365365365365365365356
16°F365365365365365365365365365

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
99% of years
28°F or colder
90% of years
24°F or colder
50% of years
20°F or colder
16% of years
16°F or colder
2% 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
1,326
Cooling degree days, base 65°F
2,733
Growing degree days, base 40°F
10,555
Growing degree days, base 45°F
8,781
Growing degree days, base 50°F
7,078
Growing degree days, base 55°F
5,480
Growing degree days, base 60°F
4,021

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January38310166
February24618226
March13458399
April41138548
May4308769
June0454904
July0518983
August0530995
September0401850
October31213647
November16165372
December32521218

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 9 km from Markham. 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 USC00410569 (Bay City Wtr Wks). Public domain.