To dry grain, temperatures above 20ºC are needed. Humidity below 65% will dry grain but the lower the humidity, the more moisture the air will take out of the silo.
Night time drying is possible if the temperature remains above 20ºC and humidity below 65%.
If you leave the fan going when the temperature drops to 18ºC and below you will start to cool the grain and slow the drying process. The next day some drying hours will be lost as the grain warms again to release the moisture. Warm grain releases moisture easily, cool grain does not. Running the fan into one silo at a time is the quickest i.e. the more litres per second per tonne the faster the process. Two silos can be done in the summer successfully, it just takes a bit longer.

After you have dried the grain and are going to store it, now cool the silo. Run the fan during the coolest part of the day but make sure the humidity is below 55%. Just on or before sunrise in the summer months is generally a good time. Automatic controllers make drying and cooling very easy. We make a very competitively priced controller for electric models only.

Cereals don't go over 50ºC or you will roast the grain and affect germination. The following notes apply except for drying temperature:

Use temperature monitor to get temperature as high as 65ºC. This is okay for sorghum. Humidity must be below 65% before you start fan. Turn off when humidity goes back to 65%. Temperature above 14ºC is the lower limit for starting fan. You can start drying straight after you have filled the silo or leave it to warm up by itself for 3 days. When putting 65ºC into the silo you have to keep a check on the sorghum at the top of the silo to make sure it is not getting too wet. If it is very wet this will block the air flow out of the silo. Take out about 2 tonne (from a 1 OOT or less from a 60T) and feel the sorghum as it flows out of the bottom outlet and as soon as you feel cold/wet sorghum shut the slide off. You will have brought the wettest sorghum from the top closer to the air inlet. Now put the dry warm sorghum back on top, this will help take up some moisture and you will have broken up the moisture barrier at the top. If humidity is low e.g. months of February and March this procedure may not be necessary, but it is worth checking on. The grain dries from the bottom up to the top. When getting a sample take it a metre down from the top and if it is okay there you will know everything below that will be lower than that right down to the driest sample at the very bottom.

Corn seems to release moisture faster than grain and consequently can cause a problem, by making the top part of the corn in the silo very wet. To dry corn, starting at 35' to 40'C. ( With heater same humidity level applies) and keep a check on the corn at the top to make sure it is not getting too wet. If it is, take some out using the same procedure as the sorghum notes.

If it is raining you don't have the fan on, except if you have been drying grain that was high in moisture. Don't leave it without some fresh air blown through. So run the fan during a warm part of the day, every two days for an hour; to blow the stale air out. If you left it for a week without putting fresh air in it would clamp together, and you would need to empty it all and put it back in again to break it up and start drying again. The same will apply to any silo full of wet grain if you don't continue the process to the end.