Marine Weather and Tide Forecast for Port St. John, FL

DISCUSSION
Issued at 245 AM EDT Tue Jul 14 2026

Today-Tonight...Pattern will be somewhat similar to yesterday, with a prevailing low to mid level offshore flow and sea breeze collision closer toward the east coast continuing to focus greatest coverage of convection across east central Florida today. Coverage of showers and storms is forecast to range from scattered to numerous (rain chances ranging from 40-60%), with this activity shifting east- southeast and offshore through the afternoon and evening hours.
Overall coverage of this activity may end up lower than yesterday, as there will be a little more drier air aloft from the Saharan Air Layer (SAL), lowering PW values to 1.7-1.9 inches today. However, this drier air and a slight increase in steering winds will continue to support strong to locally damaging wind gusts around 40-60 mph and frequent lightning in any stronger convection. While potential remains very low (<2%), can't rule out the potential for a funnel cloud or brief weak tornado with any storms that interact with the east coast sea breeze.

Highs will continue to range from near to above normal, in the low to mid 90s, with peak heat index values ranging from 102-107F. As showers and storms diminish through late evening, lows will fall to the low to mid 70s.

Wednesday-Thursday...Low level W/SW flow continues with ridge axis over the West Atlantic near to south of the area. Model guidance does show even drier air from the SAL moving into the area, with the GFS showing PW values on Wednesday dropping to as low as 1.5-1.6 inches. However, models have struggled with the amount of dry air and even NBM has been increasing PoPs slightly for this period as we get closer in time. However, for now the forecast for lower convective coverage continues, with PoPs ranging from 20-40% each afternoon/evening. The low level offshore flow and sea breeze collision will continue to generate at least isolated to scattered showers and storms across the area, with a few stronger storms still possible.

The decrease in convective coverage will only allow temps to increase, with more widespread mid 90s for max temps across the area. Drier air aloft should mix down leading to a decrease in afternoon dewpoints (as low as upper 60s/low 70s across the interior), but with the hot temps will still lead to peak heat index values 100-107F.

Friday-Monday...Mid level ridge extending from the Atlantic and across the southeast U.S. will gradually break down as trough digs southward across the eastern United States through the weekend into early next week. This will keep surface ridge axis near to south of the area. Moisture gradually rises through the period, with afternoon/evening shower and storm chances increasing and returning to more normal values (PoPs around 30-40% Friday and then 40-50% for much of the area Saturday-Monday). No relief from the July heat is in sight, with max temps forecast to continue to range from the low to mid 90s. The added humidity may even push peak afternoon heat index values a little closer to Heat Advisory thresholds (108-110F) in some spots. However, most for most areas values still look to mostly range from 102-107F.

MARINE
Issued at 245 AM EDT Tue Jul 14 2026

Boating conditions will remain generally favorable through the rest of the week and into early this weekend, outside of offshore moving thunderstorms during the afternoon and evening hours. Ridge axis of high pressure over the west Atlantic will remain near to south of the waters. This will continue winds generally out of the west- southwest during the overnight and morning hours, switching to the south-southeast into the afternoon/evening as the east coast sea breeze forms. Wind speeds are forecast to remain mostly below 15 knots, with seas 1-3 feet.

Scattered to numerous offshore moving storms will again be possible this afternoon and evening, and will be capable of producing strong to locally severe wind gusts up to 35-50 knots and frequent lightning. Coverage of storms then decrease into mid to late week, becoming isolated to scattered, but a few strong offshore moving storms will still be possible during the afternoon and evening hours.

AVIATION
(06Z TAFs)
Issued at 142 AM EDT Tue Jul 14 2026

VFR conditions outside of convection at ECFL terminals. Quiet through morning, with light SSW-SW/VRB winds picking up to 5-10 kts from the WSW-SW late in the morning. The sea breeze will develop after 17Z, shifting winds at coastal terminals ESE-SE at around 10 kts. Offshore flow will again slow inland progression of the east coast sea breeze, resulting in another collision over ECFL. Some uncertainty in convective evolution, but most guidance calls for an active afternoon-evening with initially ISO TS developing inland as early as 16Z, but most likely after 18Z, on a quick moving west coast sea breeze, increasing in coverage becoming SCT-NUM after 20Z as this activity runs into the east coast sea breeze. Guidance favors TS reaching the northern terminals (KMCO-KTIX north) first, then working south along the sea breeze collision. TS dissipate or push offshore after 23Z from north to south, with impacts lingering at the Treasure Coast terminals as late as 04Z.

PRELIMINARY POINT TEMPS/POPS
DAB 91 74 92 75 / 60 20 40 10 MCO 94 75 95 76 / 60 20 30 10 MLB 92 76 92 77 / 60 30 30 10 VRB 94 74 94 75 / 40 40 20 10 LEE 92 76 94 77 / 60 20 30 0 SFB 93 75 95 77 / 60 20 40 10 ORL 93 76 94 77 / 60 20 30 10 FPR 93 74 93 74 / 40 40 20 10

MLB WATCHES/WARNINGS/ADVISORIES
FL...None.
AM...None.