textproduct: Key West

KEY MESSAGES

- Measurable rain chances will remain low through the weekend, only up to 10% for each forecast period.

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

DISCUSSION

Issued at 1020 PM EDT Sat Jun 20 2026 Drier weather will usher in the upcoming week after pulses of showers around the island chain early this morning. In addition, GOES East nighttime microphysics observations indicate cloud cover became rather sparse across the Florida Keys waters after sunset. Along the reef, breezes slackened to light to gentle east to southeasterlies. Thus, there is higher confidence that radiative cooling will be able to lower temperatures a bit more for the interiors of the larger islands. This may offer a bit of a reprieve from the heat overnight, but only for those a bit of a distance away from the ocean.

Yesterday's 00Z KKEY balloon sampled an environment with ample moisture and untapped instability. This evening, the radiosonde traveled through a less favorable environment for showers. The overall PWAT dropped to a value slightly above the 50th percentile for the day. Measured wind speeds in the lowest 10 kft were also not impressive, below 10 knots, supporting the general stagnant flow.

However, that was not the case for Miami's 00Z sounding. That instrument measured over 2.3" of environmental PWAT. The anomalous amount of moisture and over 2.5 J/kg of CAPE were sufficient to support a pronounced thunderstorm that collapsed just north of Ocean Reef after sunset. Sensors at Carysfort Reef Light measured peak wind gusts of 43 knots along the outflow boundary while the thunderstorm's rain core collapsed. We do not have high confidence that another thunderstorm like that will form overnight. Thus, we are not making changes to the inherited forecast.

MARINE

Issued at 1020 PM EDT Sat Jun 20 2026 No watches, warnings, or advisories are in effect for the Florida Keys nearshore waters. From synopsis, a broad, weak high pressure currently extending from the central North Atlantic and across the Gulf Basin will fracture into two cells. This will lead to a weakening pressure field across the Florida Keys and surrounding coastal waters. As a result, expect light and variable winds at times continuing through Sunday night. Thereafter, the two high pressure cells will merge and briefly build, allowing breezes to freshen slightly Monday and Monday night. The high is then expected to weaken again with lighter breezes returning Tuesday.

AVIATION

(00Z TAFS) Issued at 1020 PM EDT Sat Jun 20 2026 VFR conditions will prevail at EYW and MTH for the upcoming TAF period. Near surface winds will have occasional periods of prevailing east to southeasterlies through tomorrow morning. Winds will start to veer westerly tomorrow afternoon.

PRELIMINARY POINT TEMPS/POPS

Key West 84 90 84 91 / 10 0 0 0 Marathon 84 89 84 89 / 10 10 0 0

KEY WATCHES/WARNINGS/ADVISORIES

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