I would also like to point out that many of the Allied Tactical Air strips in France were grass fields. Rain would obviously make take offs and landings rather hazardous to say the least.
Also as henkster mentioned cloud base has a lot to do with tactical aircraft operations. Any cloud base lower than 2 to 3,000 feet above the ground would make operations difficult. Also a lot of navigation at that time was visual and flying at 250 to 300 knots would have made target id rather difficult.
We had enough problems with friendly fire on clear days not to mention what would happen on days when the cloud base was close to the deck.
Regards
alfa6 ;>}
Thanks.