“Now that winter has arrived on Game of Thrones, executive producers David Benioff and D.B. Weiss felt that the storylines of the next season would be better served by starting production a little later than usual, when the weather is changing,” said Casey Bloys, president, HBO programming. “Instead of the show’s traditional spring debut, we’re moving the debut to summer to accommodate the shooting schedule.”
So there you have it, winter is finally here and the actual summertime weather is causing a drag on filming. Bummer.
The next two seasons are going to be shorter too; as the producers for the show want to cap the series at 73 hours, meaning Season 7 will be only seven episodes and Season 8 will have six. It’s not yet official though, so it’s possible they could go longer.