textproduct: Key West

KEY MESSAGES

- A moisture surge will support scattered rain and thunderstorm chances into midweek.

- 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 100-105 degrees daily, with little relief in the muggy conditions overnight. Know the signs of heat stress, take frequent breaks, and stay hydrated.

DISCUSSION

Issued at 1039 AM EDT Mon Sep 7 2026

Scattered showers with embedded isolated thunderstorms continue this morning. They were mainly concentrated north of the island chain but recently a cluster is flaring up across the western Straits of Florida. Looking at the low levels, we can see the remnants of a weak low level trough across the southeastern Gulf and Florida Keys, which has led to the activity north of the island chain. Meanwhile, an isolated and rather small shortwave is rippling along the low level ridge that is situated across the northern Caribbean. This shortwave is generally moving northeast and has entered the Straits of Florida, right where we see new convection popping up. These low level features are putting the Keys in a nebulous pressure regime, which is keeping winds generally light and variable this morning.

As we go through the day, the aforementioned shortwave will trek northeast and interact with residual low level moisture. This will be enough to allow for additional showers and thunderstorms to flair up at times. In addition, hi-res models show a southwest to west wind developing through the day which could also allow for a reverse cloud line to develop. This however, will hinge on if we can break out into some sun during the afternoon. Nonetheless, given the other features previous mentioned, opted to leave PoPs at 40 percent for now.

MARINE

Issued at 1039 AM EDT Mon Sep 7 2026

Scattered showers with embedded isolated thunderstorms will prevail across most of the Florida Keys coastal waters through the afternoon. Mariners encountering this activity can expect higher winds and seas. Outside of convection, expecting light and variable breezes that will have a tendency to want to become southwest to west during the afternoon. Given the weak pressure regime the Keys and surrounding coastal waters will remain under, we can expect light to gentle variable breezes through Tuesday night.

AVIATION

(15Z TAFS) Issued at 1039 AM EDT Mon Sep 7 2026

Scattered showers and isolated thunderstorms continue to fire in the vicinity of the EYW terminal. Any passing shower or thunderstorm will bring the potential for brief IFR/LIFR visibility along with gusty, erratic winds. Outside of any convection, expecting VFR conditions with generally light and variable winds with a tendency to becoming southwest to west in the afternoon.

PREV DISCUSSION

Issued at 501 AM EDT Mon Sep 7 2026

A mostly uneventful night into early morning for KBYX as only a few light scattered showers have been detected in the offshore waters. Temperatures along the island chain are in the mid 80s making for little relief from the day time highs of near 90. According to Nighttime Microphysics skies are partly cloudy. Marine observations across the Reef are reporting light and variable winds. Today is expected to be similar to the past few days as deep tropical moisture continues to linger in the region. MIMIC Precipitable Water is showing around 2.2 inches surrounding our area. Models suggest activity will ramp up in the early to mid morning. A afternoon cloud line development is possible as light variable winds remain light and become southeasterly.

By mid week, the elevated rain chances we have been experiencing for the past few days will return to near normal as high pressure starts to build in. High pressure will also result in a slight freshening of breezes with mid week with periods of gentle to moderate breezes with the possibility of at times fresh. Small Craft Advisory conditions are not expected at this time. Stay tuned for any updates.

PRELIMINARY POINT TEMPS/POPS

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

KEY WATCHES/WARNINGS/ADVISORIES

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