The absolute precision

In the future, it appears that the weather is for the less very precise. When he arrives in the future, Doc knows the exact second when the rain stops. Given that it's not the first time he has been at this moment in time, he could have written down the exact moment when it stops raining. But it is not, we learn a few seconds later that he's just trusted the weather report ! It also means that doc is extremely meticulous when he's got to put his watch right by the local time. Or maybe it's a 2015 watch which automatically puts right...

A changeable weather

When Doc, Marty and jennifer arrive in the future, the rain is pouring and the sky is very cloudy. You could even think at first sight that it's dark. Actually, it's only 4.29 in the afternoon.

At the instant indicated by the weather services, the cloudburst turns into a shiny, blue sky.

When Marty wants to give back the hoverboard to the little girl, we can see a perfect blue sky behind the clock tower. The following instant, when Marty is called out by the holographic newsflash, we can see that the sky becomes all of a sudden much more cloudy...