textproduct: Key West

KEY MESSAGES

- Rain chances will only reach 10% over the next several days.

- Conditions will remain seasonably warm and muggy, but we may see heat index values above 105F, particularly along the Upper Keys, through Friday.

DISCUSSION

Issued at 1035 AM EDT Wed Jun 17 2026

A few early morning showers have kept our KBYX radar busy as it has continued to detect this activity across the nearshore and offshore waters adjacent to the Middle and Upper Keys. MRMS estimates only a few hundredths of rain may have fallen along island communities while the "heavier" showers over the distant Florida Straits may have produced up to three quarters of an inch for our local marine life. As we are typing this morning update, this shower activity is diminishing quickly, and we expect our radar to be free of any showers within the next 30 minutes or so. There is no evidence of any meaningful, larger scale lift. In fact, the south-southeasterly flow may lead us to be shadowed by Cuba just like yesterday. There may also be some Saharan Air Layer (SAL) playing a role here as there is a notable dry layer around 700mb on the KKEY 12Z sounding from this morning. The inherited forecast reflects a 10% chance of rain, mainly in the morning, and this seems reasonable as the Upper Keys carry that 10% chance all day. There may be less Cuban shadow influence in that portion of our forecast area.

Of note, surface observations are reporting dew points near 80F this morning. These are values associated with exceptionally muggy air, and point to a moderate to high heat risk since the human body has a more difficult time cooling itself in these conditions. Anyone enjoying our shower-free skies today should take this into consideration. Prevent heat related illness by wearing loose, light colored clothing, drinking plenty of hydrating beverages, and taking breaks in the air conditioning.

DISCUSSION

Issued at 357 AM EDT Wed Jun 17 2026

The aforementioned ridge will continue to dominate our sensible weather through much of the next 7 days. Despite the moisture in the lowest levels across the area, we will have to contend with pockets of drier air just above the boundary layer. This combined with the deep layer subsidence, will make it highly unlikely for showers or an isolated thunderstorm to get going. The impacts instead will be the increasing heat risk. Heat index values for Tuesday reached and exceed 100 degrees and is expected to reach higher values today through Friday, especially across the Upper Keys.

A quasi-stationary frontal boundary that lies along and north of the North Gulf Coast will meander southward towards the end of the week and into the weekend. This will act to weaken the ridge and lead to slackening winds over the weekend. Winds could briefly go light and variable Saturday into Sunday before the ridge gradually re-builds and winds return solidly from the east and southeast. Meanwhile, moisture will continue to be limited along with large scale subsidence holding in place. This will keep rain chances at 10 percent at best through the foreseeable future.

MARINE

Issued at 1035 AM EDT Wed Jun 17 2026

There are no watches, warnings, of advisories in effect for the Florida Keys local waters. A weak high pressure system in the central North Atlantic will support light to gentle breezes persisting through the rest of today across the Florida Keys coastal waters. The high will begin to strengthen tonight, supporting slightly freshened breezes through the end of the work week. As a weak frontal boundary approaches the Florida Peninsula, the high will once again weaken, supporting a return to light to gentle breezes and potentially light and variable briefly, for the weekend.

AVIATION

(15Z TAFS) Issued at 1035 AM EDT Wed Jun 17 2026 VFR conditions will prevail at both island terminals, but intermittent observations of MVFR CIGs at MTH are possible during the first few hours of the TAF period due to lingering lower level clouds. Most of this cloud cover will clear out as nearby very light showers continue to dissipate. Surface winds near 10 knots will prevail out of the southeast.

PREV DISCUSSION

Issued at 1035 AM EDT Wed Jun 17 2026

PRELIMINARY POINT TEMPS/POPS

Key West 91 82 91 82 / 0 20 10 0 Marathon 88 82 89 83 / 10 10 10 0

KEY WATCHES/WARNINGS/ADVISORIES

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