I've seen other crew encourage passengers to mention this in a feedback form.. it can get really (really) uncomfortable during the day. The windows in the cabin are closed to keep direct sun out but it's still obviously like a furnace. Apparently the procedure is that the A/C will only kick in once the 2nd engine is on.
15 minutes or so after takeoff is more the temp is fine, as for for the hour or more for boarding and checks.. different story
