Weather in WITE is so ultra-simplistic. It is really lacking. And yes, I know to fix it would take some effort and therefore it will not happen, which is too bad.
1) Random weather should be based on historical weather per year (so 41-42 will (generally) be more severe than 44-45 (agree with Pelton)
2) There should be many more zones- wtf where can you have mud for 1000 miles in any direction???
3) There should be a "light mud" weather effect
My impression of the current weather is that it was done way early in the games development- just something quick and dirty so the game could be tested- and as other parts came into place and were worked on, they just kinda forgot about the weather and left it as it was.
The answer to 2 is, of course, Russia...where the accumulated moisture of 5 months of snow melts, causing fields to be flooded, and the land to be a sticky goo. But then anybody who read anything about Russia would know this.
As for light mud, well...what exactly is 'light mud'? If it rains, and wheeled traffic cannot move including artillery pieces, supply wagons, (either horse drawn or truck), officers for meetings with higher commands...and the afv's that would normally be on the front fighting have to be called back to help pull said vehicles out of the mud..does it matter if it only lasted a few days? If the luftwaffe has to airdrop chains to stranded vehicles so they can be used to pull them out of the mud, does it matter that they came from airfields that were sunny? They arent bombing Russians.
If the rain stops your supplies/fuel from reaching you at the front, where the weather is sunny.....should that be a different zone (implying that it is 'unaffected' by weather?) That is why a hex base system would be absolutely silly...and smaller granularity approaching sillyness.
Basically, if your supply line is hit anywhere by bad weather, that will bottleneck and slow down the supply reaching your troops, which will stop them from being an effective fighting force.
“My logisticians are a humorless lot … they know if my campaign fails, they are the first ones I will slay.” – Alexander the Great