Effect of weather on Barbarossa start date

[Icarus II]

There's been much discussion on how the Battle of Greece delayed the start of Operation Barbarossa, but I can't find much on the weather. Disregarding the Battle of Greece for a moment, what is the earliest date in 1941 that Barbarossa could start without getting bogged down in the spring mud?

 

[gallen95]

The Austrian author H.Magenheimer writes the following in "Hitler's War" (P 83):
What mitigated against a theoretical invasion at the end of May or in early June was the fact that many rivers in the western Soviet Union which would have to be crossed in the course of the attack, including the Bug and the Narew, were still in flood until well into June and would therefore have presented a very disagreeable obstruction .For this reason alone,an attack after 10 june appeared to be the only realistic possibility .
Magenheimer gives the following source:
Zapantis:"Hitler's Balkan Campaign,P 86 et seq.