Heat indices between 105 and 110 degrees are expected across Aventura, Sunny Isles Beach and Golden Beach on Wednesday, Aug. 12, prompting the National Weather Service to issue a heat advisory from noon to 7 p.m. for all of Miami-Dade County.
It is the second straight day South Florida has been under a heat advisory. Tuesday's warning expired at 7 p.m.
NWS Miami urged residents on X to take proper precautions before spending any time outdoors. According to the NWS, direct sunshine can add up to 15 degrees to the listed heat index, meaning anyone outside without shade could feel temperatures well above 110.
Morning lows Wednesday were already in the mid-80s, with heat indices in the 90s before the advisory window opened, WPLG Local 10 meteorologist Julie Durda reported. Lighter winds are keeping storm chances closer to inland areas west of the Turnpike, leaving coastal communities like Aventura with less cloud cover and lower rain chances.
Wednesday is also the first day of school for Broward County, the Archdiocese of Miami and Monroe County students, meaning children will be outdoors during the advisory window.
Miami-Dade's advisory threshold is 105 degrees, lower than most Florida counties, which trigger at 108 to 112 degrees. Sixty-four of the state's 67 counties were under a heat advisory Wednesday, up from 62 on Tuesday, according to USA TODAY Network-Florida reporting.
AccuWeather meteorologist Peyton Simmers said Tuesday that the prolonged heat is being driven by two factors: a Bermuda High positioned farther east than usual in the Atlantic, and a heat dome that moved east from the western U.S. and is now parked over the Southeast.
The heat isn't letting up. Forecasters warn additional heat advisories are possible each day this week as rain chances stay low and highs remain in the 90s.
Who is most at risk
Older adults, children, pregnant people, those with asthma or heart disease, and anyone who works or exercises outdoors face the greatest danger, according to the CDC. Extreme heat kills more than 700 people per year in the United States.
The CDC also warns that fans help only when indoor temperatures are below 90 degrees. Above that, fans can actually raise body temperature.
How to stay safe
Residents without air conditioning can call 211 to find cooling center locations in Miami-Dade County. The City of Miami urged residents on X Wednesday to stay hydrated, limit strenuous outdoor activity, take breaks in shade or air conditioning, and never leave children or pets in parked vehicles. The same guidance applies countywide.
For heat-related emergencies, call 911.
