http://www.journalnow.com/servlet/Satellite?pagename=WSJ%2FMGArticle%2FWSJ_BasicArticle&c=MGArticle&cid=1031783144355&path=%21nationworld&s=1037645509161
This is interesting
"The Germans have been expecting an attack further to the north. That much is clear. The weather today is better than it was yesterday but worse than that normally required for an invasion. There is quite a sea swell and it is pretty windy. Not like June at all. In that sense, we took them by surprise."
From here
http://www.dailypast.com/europe/normandylandings.shtml
OK still cant find a temp but all im reading is saying that the weather was not good at all, unseasonably cold etc...
The Germans always expected the attack to come from the area of Pas de Calais and even once the actual invasion began at Normandy many top German Officers insisted it was a feint. It may have been one of the reasons the invasion was a success. Had we met head to head with the entire German army we would have been pushed back across the channel.