textproduct: Key West

KEY MESSAGES

- A swath of Saharan dust will remain across the Keys through mid week, resulting in virtually no rain chances.

- Warm and muggy conditions will continue throughout the work week, with light and often variable breezes.

DISCUSSION

Issued at 1050 AM EDT Tue Aug 18 2026 An exceptionally dry air mass is in place across the area this morning as our 12Z KKEY sounding from this morning calculated a PWAT value of 0.87". For context, the SPC Sounding Climatology data shows a daily minimum value of 1.42". A deep Saharan Air Layer (SAL) is parked aloft, and the SAL detection graphic from CIMSS shows the highest concentration of dust extends from our area across the Bahamas and southeastward. The flow in the lowest levels of the atmosphere is light and variable, so this dust will not have the opportunity to clear out just yet. In fact, the visibility at Key West International Airport has been oscillating between 8 and 10 statute miles. To the naked eye, this drop in visibility isn't particularly noticeable, but the fact that the ASOS is detecting something in the atmosphere is pretty interesting. However, you may be able to notice a very faint, dusty brown color when looking out on the horizon. The SAL is a great indicator that our rain chances are going to be near nil today, so we'll continue to carry zero PoPs. There is an offshore boundary current working its way southward off of the southern tip of the Florida peninsula. A bowing area of clouds is associated with it, and our KBYX radar is detecting its progression across the forecast area, but there is no moisture or instability for this localized lift to trigger. The light to gentle breezes this morning will shift northerly as this boundary passes across the island chain.

Current temperatures are already near 90F, but dewpoints in the mid 70s will help to keep heat index values in the lower 100s. Our usual hot spots in the Upper Keys as well as Big Pine Key will likely hit the mid 100s at peak heating this afternoon, so both residents and visitors are encouraged to practice heat safety. No changes are needed with this morning update as the forecast is unfolding as expected.

DISCUSSION

Issued at 244 AM EDT Tue Aug 18 2026 This SAL should continue to hold its grip over the Florida Keys for another day or two before pushing further west into the western Gulf and Mexico and eventually Texas later in the week. As a result, rain chances will remain suppressed with near zero chances today and Wednesday, though a minor increase starts to occur thereafter into the end of the week with slight PoPs returning, particularly north of the Island Chain in the Bay/Gulf side waters. However, this will only be a very gradual recovery of moisture with PWAT values expected to generally still remain below daily mean values as some dry air and dust may linger. In addition, the presence of the SAL combined with a lack of precipitation coverage will continue to favor warm and humid conditions with highs in the low 90s and heat indices mostly in the 100-106 range, but some isolated higher pockets could occur mainly in the Upper Keys, so residents and visitors are encouraged to practice heat safety.

By the weekend, longwave troughing will gradually dig southward across the eastern US and drop a wavy frontal boundary into the Southeast US, which will bring enhanced moisture pooling across the northern Gulf Coast and into northern FL. As this occurs, shortwave energy associated with a weak wave along the southwestern flank of Atlantic high pressure is forecast to move near or over the Flroida Keys on Saturday, which should bring some slightly higher rain chances for the weekend compared to what will be observed this week. In addition, a more typical southeasterly flow regime may attempt to become established later in the weekend, which could bring a return of more normal rain chances for this time of the year by late weekend and into early next week.

MARINE

Issued at 1050 AM EDT Tue Aug 18 2026 There are no watches, warnings, or advisories in effect for the Florida Keys local waters. From synopsis, an atlantic ridge axis draped across the coastal waters of the Florida Keys will maintain a mostly variable wind pattern this week with wind speeds mainly less than 10 knots. However, brief increases in wind speeds may occur at times in the evening hours with winds occasionally approaching 15 knots at times, mostly near the Upper Keys, so exercise cautionary conditions could briefly occur. In addition, the presence of saharan air across the Florida Keys will keep near zero rain chances through the middle of the week with a very small increase in rain chances by the end of the week as moisture slowly recovers. The best rain chances late in the week will typically occur north of the Island Chain in the Bay and Gulf side waters, though any precipitation activity in general is expected to be isolated to scattered in nature.

AVIATION

(12Z TAFS) Issued at 1050 AM EDT Tue Aug 18 2026 VFR conditions will prevail at both island terminals with nearly clear skies briefly interrupted by FEW clouds near FL025. Light and variable surface winds will eventually assume a northwest to northerly component, but crosswind concerns are almost non existent due to wind speeds less than 10 knots. Saharan dust across the area will lead to occasional VIS Observations between 8 SM and 10 SM, but categorical impacts will not occur.

PRELIMINARY POINT TEMPS/POPS

Key West 92 83 92 82 / 0 0 0 10 Marathon 91 83 91 82 / 0 0 0 10

KEY WATCHES/WARNINGS/ADVISORIES

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