MY OPINION - daytime weddings are not formal. 1 pm
especially is not a formal time frame. The ceremony should be at earliest 5 pm to require formal wear. I would not be wearing a gown to the wedding at 1 pm. I think you could find a comfortable cool pretty short dress to wear to ceremony where at best you'll be sitting most the time, not in pictures.
Since you look like you'll have a couple hours break before the reception, I'd go to the hotel, freshen up and change into your formal party attire.

It could be one reason for the large gap in time between is so folks can formal up for the reception. I mean what are folks supposed to do with the couple hour gap?