Drink plenty of liquids. Water and diluted juices are the best. Contact neighbors and relatives who are at high risk, especially the elderly, at least twice a day in person or by phone. If possible, stay in air conditioned areas. Avoid alcoholic beverages.
Alcohol can harm one's ability to cool oneself.
In a heat emergency, one can cool down with repeated cool baths or showers, even if there is no electrical power. Avoid salt tablets. Get immediate help if a person appears to be in trouble because of heat.