textproduct: Key West

KEY MESSAGES

- A 20 to 30% chance for showers will persist through this afternoon due to the possibility of cloud line activity and lingering boundary collisions. - While highs will be seasonably warm in the upper 80s through at least mid week, lows will remain warmer than normal, providing little relief from the heat in the overnight hours.

- The next opportunity for an uptick in active weather looks to be the middle of the week.

DISCUSSION

Issued at 1020 AM EDT Mon Jun 1 2026 The first official date of hurricane season opened with a significant amount of moisture across the Florida Keys. Showers were able to develop along a lingering boundary around the Upper Keys after sunrise as highlighted by the KBYX radar. Closer to the surface, dew points along the Florida Keys are still in the upper 70s. Heat indices as measured at the Key West and Marathon airports are in the mid 90s, and there are no signs the environment will cool down tonight. Light and variable winds continue along the island chain. However, environmental winds are a bit more consistent out of the southwest to west Thus, the primary concerns are going to be a mixture of heat and cloud line activity. The morning KKEY sounding sampled an environment that, yet again, had a near record high PWAT value. The wind field was incredibly weak as well, so waterspouts may be a concern this afternoon. A dry layer that could indicate the presence of Saharan Dust was also absent in the morning sounding. Expect locally heavy rain near this afternoon's showers. Given the current conditions, we are opting to maintain the current forecast. Check back later for updates, because we may be seeing additional moisture later this week.

PREV DISCUSSION

Issued at 530 AM EDT Mon Jun 1 2026 Another warm and muggy night is almost behind us along the Florida Keys. Overnight lows only dipped into the lower and mid 80s, except near Key Largo where rain cooled air was able to bring temperatures to the upper 70s. Dew points in the upper 70s kept heat index values overnight anywhere from near 90F to the upper 90s. Over the past few hours, there has been an uptick in activity on our KBYX radar. It looks like an area of convergence around the Lower and Middle Keys ignited a couple of lines of showers with isolated thunderstorms embedded in both lines. Even though we have a generally variable wind field near the surface, the flow aloft was able to move this activity northeast to easterly. Early risers may see some a few raindrops on their way out the door this morning, but there should be a break in rain by sunrise.

As the day goes on, a few factors are at play as to whether or not there are more showers. Similar to the past few days, winds along the island chain may assume a southwesterly direction due to daytime heating. If this southwesterly wind is sustained just long enough, a reverse cloudline could develop. The skinny forecast soundings suggest that any individual shower could become an efficient rain-producer, and this goes for cloudlines too. Another factor will be colliding residual boundaries that have been noted on radar. Any boundary collision could trigger new shower activity. All of this is to say that someone is going to see rain today, it's just a matter of who? Since the Middle and Upper Keys currently have a few outflow boundaries at play, as well as the potential for afternoon showers from mainland convection in the afternoon, we'll advertise a chance of showers (around 30%) for these communities. For the Lower Keys, we're betting on the lingering activity from this morning, and once this fizzles out we may be done for the day, so we'll advertise a 20% chance for these communities.

How the middle of the week plays out will depend on the evolution of troughing down the east coast. The most recent model runs have the frontal boundary associated with this trough stalling around the middle of the peninsula. The closer that front can get, the better lift we will see in the environment, so this will impact rain and thunder chances. Either way, the best chances for showers and thunderstorms look to be on Wednesday and Thursday. This front doesn't look like it will be able to get close enough to bring drastically drier air, but knocking off a few degrees from our dew point will make the air feel just a little bit less muggy. After the parent trough had the opportunity to lift away from the area, closer to normal conditions will be able to settle in.

MARINE

Issued at 530 AM EDT Mon Jun 1 2026 There are no watches, warnings, or advisories in effect for the Florida Keys local waters. From synopsis, weak high pressure across the area will support light to gentle breezes going back and forth between southwest to northwest over the next couple of days. Near normal rain and thunder chances also expected. A weak frontal boundary may stall near the Keys coastal waters by mid week, supporting an uptick in breezes as well as rain chances.

AVIATION

(12Z TAFS) Issued at 1020 AM EDT Mon Jun 1 2026 VFR conditions prevail at EYW and MTH. Near surface winds will remain light and variable. An afternoon cloud line may form over the Lower Keys as high altitude cloud cover disperses. Showers are most likely to form near lingering boundaries when not part of a cloud line.

PRELIMINARY POINT TEMPS/POPS

Key West 91 81 91 80 / 20 10 20 30 Marathon 88 81 88 80 / 20 10 20 30

KEY WATCHES/WARNINGS/ADVISORIES

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