textproduct: Key West

KEY MESSAGES

- Moisture will linger across the region through the end of the week, supporting rain and thunderstorm chances.

- The primary threat for any stronger thunderstorms will be dangerous lightning strikes. When thunder roars, go indoors. If on a boat, stay low, or go below.

- Heat index values will range from 100-108 degrees daily with little relief from the muggy conditions overnight. Know the signs of heat stress, take frequent breaks, and stay hydrated.

DISCUSSION

Issued at 1016 PM EDT Wed Sep 9 2026 After days of light, occasionally variable conditions, light to gentle east southeasterly breezes have become established across the Florida Keys island chain. Broad surface to mid level ridging was able to become more established over the past day. Breezes were able to freshen from light to gentle to moderate across the Florida Keys waters. In the meantime, surface temperatures are on track to decrease into the lower 80s for the night, and dew points continue to linger in the mid to upper 70s. Shower coverage, while sparse in the early evening, may stay that way during the first part of the night. The 00Z KKEY sounding sampled an environment with a surprising amount of inhibition for September. However, sufficient CAPE existed in the upper atmosphere for showers to tap into. The sampled PWAT, around 2 inches, also matched CIMSS-MIMIC Layer PWAT estimates. These observations offer an explanation as to why GOES East satellite observations show a sparse amount of cloud cover across the Keys as of the early evening hours.

While weather is on the uneventful side during these early evening hours, vigorous showers near the Bahamas suggest the environment will shift to favoring showers again. Despite the inhibition sampled by the sounding, KBYX radar has detected developing showers across the waters. Convective models suggest showers will be able to redevelop over the Keys waters later tonight. The environment is still primed for showers and thunderstorms. It is also September, and the average chance for showers this time of year is 30 percent. We also have high confidence that a diurnal trend in breezes, peaking in the evening with lulls during the day, will be the norm for the rest of the week. Expect another day of easterly winds, a chance of showers, and highs near 90. September weather in the Florida Keys continues.

MARINE

Issued at 1016 PM EDT Wed Sep 9 2026 No watches or warnings are in effect at this time for the nearshore and offshore waters of the Florida Keys.

From synopsis: Ridging established across Florida resulted in gentle to occasionally moderate east to southeasterly breezes. Expect breezes to peak in the evening and overnight while lulling during the day during the next several days. A series of lower level moisture swathes will support periods of elevated rain and thunder chances.

AVIATION

(00Z TAFS) Issued at 1016 PM EDT Wed Sep 9 2026 VFR conditions will prevail at EYW and MTH for the upcoming period. Near surface winds will remain east to southeasterly near 10 knots outside of showers. Shower coverage is expected to increase after midnight, but exact times are uncertain. IFR to LIFR conditions are possible during the heaviest SHRA.

PRELIMINARY POINT TEMPS/POPS

Key West 92 83 92 82 / 50 40 60 30 Marathon 90 83 90 82 / 40 50 40 30

KEY WATCHES/WARNINGS/ADVISORIES

FL...None. GM...None.