I don't know how it is possible for it never to be above 85. We had plenty of days hotter than that with no A/C on so I know our house was in the 90's more than once.
But I had the same dilemma when out and about. All day picnics, water park, beach, etc.
I did not leave it in the car, but kept it with me and figured it was no different than when at home. it was just as hot. for some day trips, I carried it in a little cooler bag with no ice. hoping to cooler bag would keep it from heating up as much. But I am sure there is a better way.
So I guess I am just saying that I am looking for suggestions too...