textproduct: Key West

KEY MESSAGES

- Better moisture is returning with rain chances around 30 percent during the overnight hours.

- Heat will be the primary weather concern this week. Heat indices may creep towards 110 before the weekend.

- Shower coverage is expected to increase at the end of the week while a low in the upper atmosphere tracks westward across the Keys. This will be followed by a stronger Saharan Air Layer for the weekend.

DISCUSSION

Issued at 939 PM EDT Thu Jul 9 2026 A warm and modestly breezy evening is unfolding across the Florida Keys area as surface observations currently reflect temperatures in the mid to upper 80s with heat index values still near 100F. Similar to last night, moderate breezes near 15 mph are prevailing, so the air isnt going to develop that stagnant, heavy feeling that can happen when winds are light. The ASOS at in Key West has reported frequent wind gusts near 20 mph. There has been some question as to when meaningful showers will get going across the area as we are advertising a chance of showers (30%) overnight tonight, but our KBYX radar is currently detecting only a few isolated showers over the very distant Florida Straits.

However, a disorganized line of showers and thunderstorms is moving off of the northern Cuban coastline as we type this, and is tracking to the north-northwest at near 20 knots (or near 23 mph) which would put it within our marine zones within the next hour. Hi res guidance isnt finding much agreement as to whether or not this activity will be able to maintain itself as it tracks across our waters and approaches the island chain, but the guidance that resolved the complex over Cuba does show the island chain seeing some rain drops eventually during the overnight hours. GOES-19 Dust channel doesnt show a noteworthy SAL across the area, but the 00Z KKEY sounding from this evening points to some residual SAL lingering. The mean southeasterly flow in the vertical is likely advecting the tail end of the SAL out of the area, and allowing for moisture advection to nurture this activity. The moisture advection taking place across our forecast area is also notable on satellite-derived precipitable water. A swath of surface to 700 mb values of 1.3 to 1.5 inches is present across the area. All of this is to say that the inherited 30% PoPs seem reasonable for the overnight hours, so well go ahead and let that ride with the disclaimer that showers may fall apart just shy of the island chain.

MARINE

Issued at 939 PM EDT Thu Jul 9 2026 Small Craft Should Exercise Caution headlines are in place across all Florida Keys local waters due to east to southeast breezes of 15 to 20 knots. Breezes may briefly freshen to near 20 knots for a very short window of time in the westernmost portions of the Florida Straits during the overnight hours. Widely scattered showers will wax and wane throughout the overnight hours, but coverage will increase during the later part of Friday afternoon and into Friday night.

AVIATION

(00Z TAFS) Issued at 939 PM EDT Thu Jul 9 2026 VFR conditions will prevail at both terminals with only FEW to occasional SCT decks around FL025. East to southeast surface winds of 10 to 15 knots with frequent gusts near 20 knots will veer southeasterly over the first half of the TAF period. After sunrise, gusts should become less frequent. Showers are unlikely at the start of the TAF period, but chances increase to nearly 50% during the afternoon and evening. It is too early to sort out impacts with any precision, so opting to maintain a broad VCSH beginning around 18Z.

PRELIMINARY POINT TEMPS/POPS

Key West 83 92 83 93 / 30 50 40 10 Marathon 83 90 83 90 / 30 50 40 10

KEY WATCHES/WARNINGS/ADVISORIES

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