Eight people have died in the third heatwave to hit Mexico since mid-April, the country's health ministry said on Friday.
Temperatures reached a record high of 35 degrees Celsius in the capital Mexico City this week.
Seven of the victims died of heatstroke and one of dehydration between April 14 and June 12, the ministry said in a statement.
In the northeastern city of Monterrey, temperatures exceeded 40C, while water pressure was reduced in homes and an increased demand for electricity including air conditioning led to power cuts.
Wendy Tijerina, a Monterrey resident, said the heat is more intense because the city lies in an industrial zone.
"There is a lack of water, you can't bathe the children or even use a fan because they cut the power," she told AFP.
She said her family tries to drink a lot of water to protect themselves from heatstroke.
The government of Nuevo Leon state, where Monterrey is located, has limited the time children attend school to two hours a day to avoid sun.
Last year, Mexico declared a drought emergency in parts of the country as a heatwave and dearth of rain depleted reservoirs.
Authorities in some cities, including Monterrey, allowed households to access running water for only a few hours a day for several weeks.