Miami Heat Wave 'Completely Off the Charts'

There's still a week left in the month, and already it's the hottest May ever recorded in Miami as gauged by the heat index—leaving residents fearing the intense heat that surely awaits in summer. Late last week, the city's National Weather Service issued a heat advisory, the first for the month of May in at least 15 years, per Fox Weather. In the five days leading up to Monday, "four new high daily average temperature records and record-high humidity levels" were set, per the Miami Herald. "It's completely crazy, what just happened," Brian McNoldy, a senior research scientist at the University of Miami, tells the New York Times, referring to weekend heat index values of 112 degrees. That's "a stunning six degrees hotter than any previous May heat index recorded," per the Herald.

"Stepping outdoors felt like walking into a broiler, even well into the night," per the Times. Sunday's high temperature, not taking into account humidity, was 96 degrees, a record for the day. Nighttime temperatures were hardly better, averaging 89 degrees to tie for the third-highest daily nighttime average temperature ever recorded. In a post on X, McNoldy noted Miami's heat index—which combines temperature and humidity—has already spent more time above 108 degrees than in "any other entire year" except for 2023. "These temperatures in May are completely off the charts," he tells the Herald. Such heat and humidity "would've been exceptional even in another three months."

As warming air under a high-pressure ridge met moist air from the southwest, the heat index in Key West hit 115 degrees on May 15, beating the previous record for the day by 17 degrees. The Herald notes such "early-season heat events have some of the highest rates of heat illness and heat-related deaths because people are not prepared for it." With rainfall in the forecast, relief is coming in the short term. As for the long term, "who knows," McNoldy tells the Herald. (Gov. Ron DeSantis last week signed legislation stating Florida doesn't have to consider climate change when creating policy, receiving pushback from a meteorologist.)