Marine Weather and Tide Forecast for Marathon, FL

DISCUSSION
Issued at 422 AM EDT Mon Jun 15 2026 The warm and humid days are upon the Florida Keys. Dew points across the island chain continue to be in the low to mid 70s.
Lower temperatures are possible along the larger islands of the Florida Keys this morning due to radiational cooling allowed by light winds and mostly clear skies. A thermometer at Big Pine Key reported a temperature of 76 F, and the environment cooled to 80 F at the KKEY weather station. GOES East nighttime microphysics scans identify very sparse cirrus cloud and an occasional shallow cumulus across the Keys coastal waters. CIMSS PWAT estimates indicate a slightly lower PWAT than observed over the past few days, around 1.7 to 1.8 inches, though there is still more than enough moisture for showers. The issue is a source of lift, and that will be the forecast challenge today.

Surface analyses indicate the Atlantic High is very distant from the Florida Keys, near the Azores. The primary ridge axis extends across the Atlantic towards the Keys. Our winds have been light to gentle in response, and subject to slight changes in the local environment. A southwesterly trend is expected today, indicating a reverse cloud line may develop this afternoon. Meanwhile, upper level winds continue to support sinking air in the upper atmosphere. The environment just does not favor extensive shower activity. Today, keeping the 10 percent chance of showers due to the cloud line activity.

Looking ahead, the most notable change to the forecast pattern may start mid-week. Model ensembles show the Atlantic High able to rebuild and shift west towards Bermuda. Breezes would be able to freshen somewhat and shift southeasterly. Slightly stronger breezes would limit cloud line formation. Unfortunately, this pattern shift would not help the heat and humidity. A lack of cloud cover, continuous daytime heating, and persistent southeasterly winds near the surface mean the heat will be a concern throughout the week.

MARINE
Issued at 422 AM EDT Mon Jun 15 2026 No watches, warnings, or advisories are in effect for the Florida Keys coastal waters. From synopsis, light to gentle breezes will persist through the middle of the week across the Florida Keys coastal waters. Starting Tuesday night to Wednesday, the Mid- Atlantic high will begin to strengthen and support slightly fresher breezes through the end of the week. Breezes will generally be southerly and trend southeasterly after Wednesday.
Shower and thunder chances are expected to remain very low through the forecast period. The greatest chances for showers would be in the nearshore waters off the Lower and Middle Keys in the late morning and early afternoon as island cloud lines.

AVIATION
(06Z TAFS)
Issued at 422 AM EDT Mon Jun 15 2026 VFR conditions will prevail at EYW and MTH through the upcoming TAF period. A broken cloud line may form in the afternoon, in the vicinity of the Lower and Middle Keys, but impacts to VIS and CIGs would be brief. Near surface winds will be generally light with variable periods possible.

PRELIMINARY POINT TEMPS/POPS
Key West 90 81 91 82 / 10 10 10 10 Marathon 88 82 88 82 / 10 10 10 10

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