Weather INnovations Incorporated

News

	Jan 23 - WIN Job Openings
	Jan 16 - Weather INnovations Inc. Celebrates 5-Year Milestone
	Dec 1 - Many Farmers’ Fields Submerged After Record-Breaking Rainfall
more...

Search

Search this Site..

Crop Heat Unit

Crop Heat Units are calculated on a daily basis, using the maximum (Tmax) and minimum (Tmin) daily air temperatures, measured from midnight to midnight, in degrees Celsius. The Crop Heat Unit (CHU) system is used to assist farmers to select the most suitable hybrids and varieties for their area.

The following equation is used to calculate daily CHU:

Daily CHU = (Ymax + Ymin) ÷ 2

where

Ymax = (3.33 x (Tmax-10)) - (0.084 x (Tmax-10.0)²)
(If Ymax < 0, set Ymax = 0)

and

Ymin = (1.8 x (Tmin - 4.4))
(If Ymax < 0, set Ymax = 0)

The Crop Heat Unit ratings are based on the total accumulated crop heat units (CHU) from the season start date to season-ending date.

A standard start date (date to start accumulating CHU) of May 1 is used across the province of Ontario. Read More

The season-ending date (date to stop accumulating CHU) is the earlier date of either:

the first occurrence of -2 °C; or
the date when the 30-year average daily mean air temperature dropped to 12 °C (or lower).

Maps between May 1 and Oct. 15:

Current CHU Accumulation - The CHU accumulated to today, from a start date of May 1.
10 Day Forecast of CHU Accumulation - The predicted CHU accumulation for 10 days from now.
Predicted CHU Seasonal Accumulation - The predicted CHU accumulation at the end of the season. The season-ending date (date to stop accumulating CHU's) is the date when the 30-year average daily mean air temperature dropped to 12°C (54°F) or lower.
CHU Deviation - Current vs. Normal - The difference between the current CHU accumulation and the 30 year normal for the current date.