Twenty-one senior citizens died in Egypt as a result of Sunday's heat while 66 experienced stress, the Health Ministry said on Monday.
The ministry called on citizens, especially the elderly, people with chronic disease or special needs and children, to avoid direct exposure to sunlight, particularly at noon, in an emailed statement.
It also advised citizens to avoid going out of the house, except in case of extreme necessity.
This summer, Egypt has been hit by brutal heat, especially in the past few weeks.
The temperature peaked to 39 degrees Celsius (102 degrees Fahrenheit) in the capital Cairo, on Sunday.
The majority of the people who died because of Sunday's heat were in Cairo, where 15 people died, the ministry said. The rest were in Matruh, which borders Libya and Qena in Upper Egypt.