
You may want to talk with the pilot. He may not be comfortable hovering on a hot summer day with a full load on board. The helicopters performance is reduced in hot weather vs cold, he will most likely be at lower altitudes for better images, and the thought of having to autorotate over Boston in a near capacity situation on a hot summer day might give him the willies. I know it would me

Fall (or spring) would being colder weather, better performance, clearer skies with less haze, and some nice foliage as a bonus. But I agree, summer brings some nice sunsets due to the haze. Tradeoffs, tradeoffs....
He's the one that suggested July as well. So while you may be very well versed in helicopters and such, he has the ultimate say. If he's suggesting, i'm going to guess he's comfortable.