Bin weather: will the next two days’ air dry your grain, or wet it?

Pick your town and describe the bin. From Environment Canada’s hourly forecast, this shows when running the aeration fan would dry the grain, cool it, or put moisture back, for the next two days.

By Ruslan Glick, Winnipeg · Updated 21 October 2026

Nearest town

Crop

Grain moisture, %

Grain temperature, °C

Use the moisture from your tester or the elevator’s sample. The grain temperature, from a probe or cable, lets it show the hours that would cool the bin.

How it works

Grain slowly settles at a moisture set by the air around it: its equilibrium moisture content, which depends on the air’s temperature and humidity and on the crop. Air that would settle your grain below its moisture now dries it as the fan pushes it through; air that would settle it above puts moisture back. For each forecast hour this works out that moisture for your crop, against your grain:

Dries: The air would settle the grain at least a full point below its moisture, and the air is at least 5 °C. Below about 5 °C air holds so little water that natural-air drying all but stops.
Cools: The air is at least 5 °C colder than the grain, and isn’t putting moisture back.
Holds: Within a point of what the grain has: too close to call either way.
Wets: The air would settle the grain at least a full point above its moisture.

Facts from the forecast, not a guarantee. The forecast can be wrong, which is why the last day of readings at the nearest station sits beside it. And this is the air going into the bin, not what’s happening inside it: a full bin takes days to change, and its hot spots can’t be seen from here. It never says your grain is safe. Check your bins.

Sources and method

Forecast: Environment and Climate Change Canada’s High Resolution Deterministic Prediction System (HRDPS, 2.5 km), 2 m air temperature and relative humidity through MSC GeoMet, in 3-hour steps for the next two days, from the latest model run. Used under the ECCC Data Servers End-use Licence.
Last day measured: Environment Canada’s hourly climate data at the nearest station with temperature and humidity, about a day behind real time.
Equilibrium moisture, worked out from published equations: for hard red spring wheat and yellow dent corn, ASAE Standard D245’s Modified Chung-Pfost equation with its coefficients as published in the University of Arkansas Division of Agriculture Grain Management Toolkit; for canola, the equation Muir and Sinha fitted to Pixton and Henderson’s data for Candle rapeseed at 5 to 35 °C (Canadian Agricultural Engineering 28: 45–49, 1986). These are averages from lab measurements of older varieties: treat them as a guide, which is why an hour only counts as drying or wetting a full point past the grain’s moisture. Other crops are added once there’s a second open source that agrees.
Straight, tough and damp: the Canadian Grain Commission’s Official Grain Grading Guide, moisture specifications.

Were you paid right on your last grain settlement?

Send me a photo of the settlement, and the contract if you have it. Within a day I’ll email you back what each line is, what’s worth asking the buyer about, and any grade or payment deadline that’s still open. Free, no account.

Ruslan Glick, Winnipeg. Not a farmer, so I check against your contract and the grain rules, not opinions. Top Crop Manager wrote about GrainPosition.

Email me a photo of it