The temperature came as a broad area of high pressure brought extreme heat to Florida and other parts of the Southeast. According to Newsweek, the combination of drier air, fewer clouds and offshore winds reduced several of the cooling influences that usually prevent temperatures in coastal South Florida from climbing to 100°F.
Why 100°F Is So Unusual in Miami
Miami is known for hot and humid summers, but its coastal location normally limits how high daytime temperatures can rise. Air moving inland from the Atlantic Ocean frequently provides a cooling sea breeze, while afternoon thunderstorms can interrupt heating before temperatures reach extreme levels.
Tuesday developed differently. According to CBS News Miami, a west wind prevented the usual ocean breeze from forming along the coast, keeping the metropolitan area under hotter air throughout the afternoon. Temperatures climbed through the 90s before Miami officially reached 100°F.
Newsweek reported that drier air was also mixing downward beneath a strong area of high pressure. With reduced cloud cover and less thunderstorm activity, the atmosphere allowed temperatures to continue rising later into the day.
The reading was about nine degrees above Miami’s average mid-August high of roughly 91°F. Despite numerous heat waves, hurricanes and unusually warm summers over the past eight decades, the city had not returned to 100°F since July 21, 1942. That earlier reading had remained Miami’s all-time high for 84 years. Weather records for the city date to the summer of 1895, according to CBS News Miami, meaning the two 100°F observations stand apart across more than 130 years of recorded temperatures.
Heat Dome Keeps Dangerous Conditions Across South Florida
The record-tying temperature occurred while a heat dome was affecting Florida and much of the southeastern United States. A heat dome develops when a large area of high pressure traps hot air below it. As that air sinks, it compresses and warms, while cloud development and rainfall become less likely.
Conditions remained hazardous across South Florida on August 19. According to Newsweek, a National Weather Service heat advisory was still in effect, with maximum heat index values expected to range from 105°F to 112°F. The heat index reflects how hot conditions feel to the human body when humidity is considered alongside air temperature.
Health and weather officials advised residents to stay hydrated, reduce strenuous outdoor activity during the afternoon and spend time in air-conditioned places when possible. CBS News Miami also reported recommendations to check on children, pets and elderly neighbors who may be more vulnerable during periods of intense heat.
Some relief was expected later in the week. Forecasts cited by both sources indicated that a pattern change could allow afternoon thunderstorms to return to South Florida, including coastal areas. Those storms were expected to provide some afternoon cooling and rainfall after the period of exceptional heat.
