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Heat Advisory Issued in South Florida Amid Sargassum Invasion

Sargassum Seaweed on Florida Beach

News Summary

The National Weather Service has issued a heat advisory for South Florida as temperatures are expected to exceed 100 degrees Fahrenheit. Residents are urged to stay hydrated and take precautions during the advisory period. Concurrently, South Florida beaches are facing an influx of record-breaking sargassum seaweed, creating discomfort for beachgoers due to its unpleasant odor. The situation is complicated by ongoing Saharan dust in the area, which may affect weather patterns through the weekend.

Florida

The National Weather Service has issued a heat advisory for South Florida effective July 21, 2025, as “feels like” temperatures are projected to reach the triple digits. The advisory will be in effect from 12 p.m. to 6 p.m. on Monday, with the heat index expected to hover around 105 degrees Fahrenheit in Broward and Miami-Dade counties. Residents in the Florida Keys should also prepare for high temperatures, with “feels like” values expected to rise to 102 degrees, although this region is not officially under a heat advisory.

Such advisories are issued when heat index values reach 105 degrees or higher and persist for at least two hours. The current hot conditions are attributed to rising moisture from the mid-Atlantic along with a persistent area of high pressure located over the Gulf. While Monday’s forecast shows susceptible temperatures, the chance of rain stands at only 20%, with afternoon highs predicted to settle in the low 90s.

During the heat advisory, residents are urged to take necessary precautions. Staying hydrated is essential, along with seeking shade or utilizing air conditioning during the hottest parts of the day. For individuals that must be outdoors, taking frequent breaks in shaded or cool areas is highly recommended.

Relief from the oppressive heat is expected as rain returns from Tuesday to Thursday, potentially alleviating the extreme temperatures with promising opportunities for heavy downpours. However, as the week progresses towards Friday, forecasts indicate the resurgence of Saharan dust and drier air, which will likely lead to a decrease in rain chances and potentially push temperatures back up into the low 90s, with “feels like” temperatures again reaching the 100s.

Record-Breaking Sargassum Invasion

In tandem with the heat advisory, South Florida beaches are simultaneously grappling with an invasion of record-breaking blooms of sargassum seaweed, specifically along the shorelines in Dania Beach. The brown seaweed creates an unpleasant environment, releasing a sulfur-like odor reminiscent of rotten eggs when decomposing. Witnesses have reported significant areas of the coastline being covered by sargassum, altering the landscape from the usual pristine white sands.

This recent sargassum issue isn’t unprecedented, as similar buildups have been recorded in previous months, particularly in April and May. The current influx of sargassum has been facilitated by ocean currents and swells that have transported the seaweed close to the Florida shore. Larger concentrations of sargassum can still be found primarily in the Caribbean Sea, Gulf of America, and tropical regions of the Atlantic, though local beach conditions can fluctuate unpredictably.

Despite the unsettling smell, the Florida Health Department has stated that the sargassum is largely harmless to humans. Some marine organisms that may inhabit the seaweed can cause skin irritations. Nonetheless, sargassum plays a beneficial role in the ecosystem by providing food and shelter for various marine species.

Weekend Weather Outlook

As the weekend approaches, hazy skies are anticipated due to the ongoing presence of Saharan dust, which may further diminish rain possibilities. Monday’s weather forecast predicts mostly sunny conditions, combined with a slight 40% chance of rain and a high reaching 91 degrees Fahrenheit. Residents are encouraged to stay vigilant and prepare for the combination of heat and environmental changes caused by the seaweed blooms this summer.