On modifying weather and turn's end, many players have the same opinion, raisonning that it is impossible to change the length of the month or summon good or bad weather by magic, but it is a matter of taste and perception of the game mechanisms
For example, one can wifzen that :
DDay was a situation were Germany had checked that the next weather roll was 1 (Storm) and no invasion could occur this impulse but the allies took the risk and changed it to rain, with -1 odd level. This simulates better weather forecasting on the Channel for one side (weather comming mainly from the west Atlantic).
IMHO there was no rain during DDay itself, but the naval and air bombing was mostly innefficient (like in rain) and the troops were subject to sea sickness because of the previous storm
In M/J 41, Germany had initiative and attacked by surprise on the nearly last impulse (21 june), but changed the turn end to insure that USSR could not react this turn (Stalin out of office for several days), allowing for a double move and a major breakthrough in July
"Nicht kleckern, klotzen!" - Guderian