textproduct: Key West

KEY MESSAGES

- A moisture surge will support elevated rain and thunder chances through the Labor Day holiday weekend.

- 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 indices will approach the mid 100s daily, with little relief in the muggy conditions overnight. Know the signs of heat stress, take frequent breaks, and stay hydrated.

AVIATION

(18Z TAFS) Issued at 207 PM EDT Fri Sep 4 2026 While VFR conditions will prevail across the island terminals through 18z Saturday afternoon, elevated low-level moisture will support occasional showers in the vicinity of each terminal at times. The focus of activity maybe during the late evening hours, then again Saturday morning, although confidence in timing is low at this time. Have included a general mention of VCSH for now, and this will be reevaluated for the 00z TAF issuance.

PREV DISCUSSION

Issued at 1130 AM EDT Fri Sep 4 2026 CIMSS satellite-derived total precipitable water analysis highlights the eastern, moist side of an inverted trough currently progressing across the Florida Keys. The 12z morning sounding at KEY sampled an uninhibited, moderately unstable surface-3 km environment, with southeasterly mean steering flow. Local Doppler radar continues to highlight waxing and waning scattered showers and thunderstorms in this mean flow, occasionally advecting across the Florida Keys. Outside of this activity, skies are mostly sunny across the Keys, with temperatures approaching 90F at most island communities.

For the rest of today, expect more of the same, with occasional showers and thunderstorms, with plenty of breaks in convection at any given location. As the aforementioned trough continues to progress westward and the North Atlantic ridge slowly builds in the evening hours, breezes will modestly freshen, with associated speed convergence possibly leading to a bit of an uptick in activity. We will monitor these trends, as we kick off the Labor Day weekend in the Florida Keys. Available convective allowing model (CAM) guidance supports this evolution, and we will continue to advertise mid-level chance PoPs through the early evening. No changes proposed to the inherited forecast.

MARINE

Issued at 1130 AM EDT Fri Sep 4 2026 No watches, warnings, or advisories are currently in effect for the Florida Keys waters. However, scattered thunderstorms will occasionally push through the marine zones through the weekend. The primary threat for any storm will be dangerous cloud to surface lightning strikes.

From synopsis, the western periphery of a weak North Atlantic high will remain in loose control of the Keys coastal waters for the next few days. Light to gentle, occasionally moderate, east to southeast breezes overnight through morning will become light and variable at times during the afternoon and evenings. In addition, the overall flow will keep low-level moisture in place across the region, with seasonally normal rain and thunder chances.

KEY WATCHES/WARNINGS/ADVISORIES

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