NWS warns of heat index near 105 as island showers loom in Keys

A dry pattern is setting up across the Florida Keys, but it will not feel dry. The National Weather Service in Key West said island cloud line showers may form in the late morning to early afternoon through Monday, while winds are forecast to collapse and remain light for most of the week. With humidity and heat running high, heat indices approaching 105 degrees are possible, turning routine outdoor work, school activities and errands into a health hazard.

Forecasters said the Keys will stay seasonably warm and muggy, with heat index values approaching near 100 degrees each afternoon through early next week. Any developing island cloud line could also bring waterspouts, adding another risk for boaters and anyone watching the weather from the water or shoreline. The worst conditions are expected around the late morning and afternoon hours, when the combination of sun, moisture and weak winds can make it harder for the body to cool itself.

The National Weather Service said heat index values of 105 to 110 degrees for at least two consecutive days can trigger alert procedures. That threshold matters in the Keys, where temperatures are already running unusually warm. Key West recorded the warmest May on record in 2026, tying 2024 with a monthly average of 84.7 degrees, and the warmest spring on record with a March-April-May average of 80.5 degrees. Temperature records in Key West go back to July 1872.

Health officials say older adults, young children and people with chronic medical conditions face the highest risk from heat-related illness and death, along with outdoor workers and people without access to air conditioning. The Centers for Disease Control and Prevention says more than 700 people die from extreme heat every year in the United States, and symptoms of overheating can include muscle cramping, unusually heavy sweating, shortness of breath, dizziness, headaches, weakness and nausea.

Monroe County Fire Rescue is trying to keep that risk in front of residents with five Beat the Heat events across the Florida Keys this summer. One session was held June 13 at Big Pine Key Community Park from 10 a.m. to 11 a.m., part of the county’s broader push to get people thinking about hydration, shade and timing before the hottest part of the day arrives. The message from the Keys’ weather and health officials is the same: when the wind falls off and the humidity climbs, even a coastal island setting can become dangerous fast.