(In game terms rain means several things. First, there will be no air drop and no air support for the paratroopers. Also movement costs more unless the units are in column on a road. And most important there is a negative modifier to all combat.)
September 19th 1944:
The skies open up and the rains come and do not let up. The drop scheduled for today is pushed back until the 20th and the already soggy ground becomes a virtual morass.
The Red Devils following up on their plan to switch goals from the main bridge at Arnhem to the rail bridge push south. They get there before the Germans can really react and are able to improve the bridge such that it can support vehicular traffic. There is many a back slap and "Well done, Old Chap" in thanks to the engineers who make that possible.
The paratroopers are shouldering their way forward to get to the other side of the river. If they wish to hold the bridge they must form a defensive perimeter. The Jerries won't be pleased once they hear the news.
However, the news is already out and Herr Spindler and his screaming SS Fanatics have already arrived on the far shore. They exact a heavy heavy toll upon the Tommies exposed on the bridge and the far bank. If their own withering fire wasn't enough, they call in artillery support from the divisions guns which have arrived and set up a firing position to the East.
No Brits make it to the far shore. Lets hope half a bridge is better than none.
Meanwhile the heavy guns of the Hohenstaufen division have taken positions overlooking the landing zone the 1st Airborne has been using to receive supplies. With their reduced strength and need to keep what ground they have by the bridge, they cannot form an effective counter attack. God help any future drops on that field.
West of the city things are no better. The units of Von Tettau are belligerent and numerous. Nobody can doubt the bravery of the glider pilots who block the road junction at Heelsum but their fate is sealed. If the rain should clear, they are sure to be surrounded and destroyed.
To the south, the rumble of tanks is heard. XXX Corp has made the scene and they drive as fast as they can for the city of Nijmegen and the bridge across the Waal. Now to be clear, "as fast as they can" means about as fast as you can in bumper to bumper traffic on your commute to work. Not quite as fast as one would like. And what would a traffic jam be without at least one moron making things worse? The award for "Bonehead of the Day" goes to the 82nd's Recon Jeeps who spent half the day jamming up the Club Route right outside of town.
In the wet and cold streets of Nijmegen, the 82nd Airborne has gotten up close and personal with the Germans of the Frundsberg Division and Korps Feldt who make a formidable defense. There's no other way than brutal hand to hand combat for the All Americans to move forward with any efficiency. The have success but not without the reduction of some of the most fierce of their fighting units. It is only at sunset that lead elements of XXX Corps enter the city to lend a hand.
That sneaky armored unit of Feldt's Korp has squatted down right at the end of the Club Route and takes pot shots at the vulnerable armored units as they get to town. The rain has had one beneficial effect in that his opportunity fire has been mercifully ineffective.
The dawn is just a few hours away and both sides consider the prospects for tomorrow. Much depends on the weather. Continued rain will only serve to slow things down. It seems likely XXX Corp will get over the Waal but farther south around Groesbeek, the Germans have been cautious. Building up a significant force. Clear weather will bring a major assault and if they over run the landing zones they may push on to cut the Club route south of Nijmegen.
In Arnhem, things are bleak for the Airborne unless XXX Corps gets there with alacrity. Their armor and infantry will make mince meat out of Spindler's damnable SS...if they can only arrive in time.