The house's external paint should be in lighter colour preferably white. If possible paint you roof with white paint as well. The lighter colors reflects sunlight hence the walls & roof do not heat up and there will be less heat transfer to internal walls. Keep the air circulating, meaning one or two exhaust should be working with at least one window of each room open. Make sure that kitchen exhaust is working properly. In short avoid heat transfer and keep the air circulating.
If it doesn't work buy some mangoes chill them and enjoy eating, that's what summer is for