More than five weeks remain before summer’s official start, but preparations for extreme heat have been underway for many months in parts of the country hit hard by last year’s sweltering conditions.

“We prepare for heat year-round in Phoenix,” Mayor Kate Gallego said. “It’s something that we know is coming, so we have to think about it even on the coldest day of the year.”

But last summer was especially severe — Phoenix, for example, endured 31 consecutive days of high temperatures at or above 110 degrees Fahrenheit, the city breaking a previous record of 18 days set in 1974. At least 645 people in Maricopa County, which includes Phoenix, died from heat-related causes in 2023, a 52% increase over the previous year, according to the county’s Health Department.

The 2023 heat waves revealed how challenging it can be to cope with extreme temperatures for weeks on end, even in places where residents are accustomed to warm weather. And the months ahead are expected to be just as hot — if not hotter.

That has prompted cities across the South and the Southwest to re-evaluate how best to keep people safe — and alive — this summer. Some have launched new initiatives aimed at increasing shade in public spaces, strengthening health care systems to deal with victims of heat waves and doing outreach with outdoor workers, homeless populations and other vulnerable communities.