textproduct: Key West

KEY MESSAGES

- Moisture will linger across the region through the start of the weekend, 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 Thu Sep 10 2026 Rounds of showers and thunderstorms continue to form across the Florida Keys waters this evening. Residents in the Lower Keys could look off towards the Outer Gulf waters and see extremely vigorous lightning complexes near the Towers. The KKEY 00Z sounding sampled an environment with a PWAT safely above the 90th percentile for the day. Moisture was plentiful through 600 mb, and the amount of CAPE calculated was in excess of 3000 J/kg. It is not shocking that thunderstorms capable generating gusts in excess of 34 knots were able to form. Outside of showers, gentle to moderate breezes persist along the reef. Winds are generally east to southeast. Overnight, expect the weather to be somewhat similar to what has been observed the past few days. Lows across the Keys are on track to be in the lower 80s, humidity elevated, with a chance of showers and thunderstorms.

Water vapor satellite imagery from GOES East, as well as the 700-500 Advected Layer Precipitable Water, highlight a shallow plume of drier air moving towards the Florida Keys waters late tonight. There are a couple of forecast challenges that come from this feature. The dry layer may limit shower development tonight, or the intrusion of dry air will increase the amount of ambient instability in the environment. Convective models have not been resolving showers and thunderstorms overnight, but prior model runs also did not show development of the previously mentioned thunderstorms over the Gulf. Low to mid level winds in model ensembles were slightly anticyclonic, and thus opting to leave PoPs at 30 percent overnight. The lull in shower activity is not expected to stay for long. Moisture is about to return after sunrise, so brace for another day of hearing thunderstorms over the water.

MARINE

Issued at 1016 PM EDT Thu Sep 10 2026 No watches, warnings, or advisories are in effect for the Florida Keys Coastal waters.

From synopsis: Ridging across the southeastern United States and Florida will maintain gentle to moderate east to southeasterly breezes. Expect breezes to peak in the evening and overnight while lulling during the day. A series of lower level moisture swathes will support periods of elevated rain and thunder chances through the remainder of the week and into the weekend.

AVIATION

(00Z TAFS) Issued at 1016 PM EDT Thu Sep 10 2026 VFR conditions will prevail at EYW and MTH for the upcoming period. Near surface winds near 10 knots are expected for both terminals. The environment is primed for showers and thunderstorms, but the timing of rainfall at both sites is very uncertain. Statistical guidance and convective models suggest 15Z, around 11 AM, as the most likely time VCSH would become widespread.

KEY WATCHES/WARNINGS/ADVISORIES

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