Marine Weather and Tide Forecast for Marathon, FL

DISCUSSION
Issued at 1544 PM EDT Thu Oct 8 2026 A complicated weather pattern set up from the southeastern United States to the Lesser Antilles over the past few days. Hurricane Isaias, understandably, drew the most attention from forecasters and the media. However, this tropical cyclone is not the only feature modifying weather across the Florida Keys. Water vapor satellite observations highlight a stalled frontal system across central Florida. Upper level satellite imagery also identifies active showers southwest of Hispaniola as part of a Tropical Upper Tropospheric Trough. Meanwhile, shower activity is sparse across the Keys waters. What happened, and why are showers so inactive?

Currently, these three features are inducing sinking motion across southern Florida. Outflow from Hurricane Isaias is running into air directed north by the previously mentioned TUTT and sinking over the Keys. Meanwhile, persistent southerlies mean the Keys are in the lee of the Cuban landmass. In a surprising turn, a Cuban Shadow was not observed by the 18Z sounding. Cumulus clouds were finally able to bubble up north of the island chain in the afternoon hours. In spite of these nearby showers, widespread convection is still unlikely because of the drier air aloft. Tonight, expect another relatively uneventful evening across the island chain.

Dry conditions are not expected to last through the weekend.
While Hurricane Isaias moves towards the northern Gulf Coast, the TUTT will continue moving west. The region of sinking air will be replaced by a region that more favorable for showers. At the same time, a weak low level wave will move north towards the Keys this weekend. Statistical models have shown consistent hints that shower chances will increase during the first half of the upcoming weekend. A drier pattern is expected to set up across the Keys after this pulse of shower activity. Mid-week, the pattern gets a bit more complicated. Some statistical models suggest a weak frontal system could move towards the Florida Keys. Forecast uncertainty is still high during this period of time, so check back before making any plans.

MARINE
Issued at 1544 PM EDT Thu Oct 8 2026 A Coastal Flood Statement is in effect for the Florida Keys.
Boaters should be aware of less clearance under fixed bridging around times of high tide. While no watches, warnings, or advisories are in effect for the Florida Keys nearshore and offshore waters at this time, breezes are expected to freshen to moderate to fresh over the western waters in response to Hurricane Isaias. Small craft should exercise caution headlines may be required for the western zones of the Florida Straits and the Outer Gulf waters.

From synopsis: Hurricane Isaias, currently over the southwestern Gulf waters, is expected to move towards the North Gulf Coast over the next few days, strengthening as it does so. Enhanced swell generated by the hurricane will increase wave heights in the western Florida Straits and Gulfside waters tonight through the first half of the weekend. A stationary front remains draped across north- central Florida which will slowly drift southward infringing on the surface ridge to its south. Breezes are expected to freshen before the weekend in response with moderate to fresh breezes possible in the western waters. A plume of moisture will also move into the Florida Keys at the same time and increase shower and thunderstorm chances.

AVIATION
(18Z TAFS)
Issued at 1544 PM EDT Thu Oct 8 2026 VFR conditions will prevail at EYW and MTH for the upcoming TAF period. Winds are on track to slowly back southeasterly and freshen towards the 10 knot to 10 to 15 knot range. Cloud cover will wax and wane, but CIGs are unlikely to develop.

CLIMATE
On this day in 2020, the daily record warm low temperature of 83F was recorded in Key West. Temperature records for Key West date back to 1872. On this day in 2012, the daily record warm low temperature of 82F was recorded in Marathon. Temperature records for Marathon date back to 1950.

PRELIMINARY POINT TEMPS/POPS
Key West 82 88 82 88 / 20 30 70 40 Marathon 82 88 82 89 / 20 40 70 40

KEY WATCHES/WARNINGS/ADVISORIES
FL...None.
GM...None.