Some canola is coming off very dry — 5-6% moisture. Canola at 8% moisture is considered safe for long term storage. Canola at 6% is even safer. (Although it can still heat if very hot when stored.)
Canola seed can absorb more moisture if left in the field during a rain. Both 6% and 8% moisture canola can be safely stored when cool, however increasing moisture from 6% to 8% would add the weight of a bushel/acre to a 50-bushel crop. Growers may not choose to leave a crop out in the rain, but this situation may influence which crop you combine first.