Depending on your region of the country, and the heat you’re experiencing, take care to perform outdoor summertime activities while staying hydrated, and for short intervals-while taking breaks to cool down.
Maintain the HVAC system; clean out the condenser if it has leaves or other debris in it, clean the coils, flush the system and have it checked.
Inspect and repair exterior damage. Paint exterior as applicable.
Clean gutters, and ensure proper ventillation in the home.
Inspect and maintain outdoor spaces such as kitchens, patios, decks, driveways, pools, etc.
Inspect for pests, take preventative measures and remediate as necessary
Maintain yard cleanliness: regularly clean up debris and standing water, encourage natural predators like bats, birds and beneficial insects. You can plant flowers that attract beneficial insects, and provide bird and bat houses. If you have fruit trees, keep in mind that snakes will help keep the rodents under control.