textproduct: Key West

KEY MESSAGES

- A swath of Saharan dust will remain across the Keys through mid week.

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

DISCUSSION

Issued at 244 AM EDT Tue Aug 18 2026 The 18/00Z KEY RAOB shows a remarkably dry air mass is in place with PWATs sampled at just 1.12 inches, nearly a tenth below the daily minimum of 1.21 inches for mid August. There is only one logical culprit that is responsible for this bone dry value and the culprit is of Saharan origin. Recent CIMMS analysis shows an extensive area of this Saharan dust stretching from the SW Atlantic/northern Caribbean across the Straits of FLorida and southern FL peninsula and further westward into the southern Gulf waters. 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 244 AM EDT Tue Aug 18 2026 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 kts. However, brief increases in wind speeds may occur at times in the evening hours with winds occasionally approaching 15 kts at times, 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

(06Z TAFS) Issued at 244 AM EDT Tue Aug 18 2026 VFR conditions will prevail at both Island Chain terminals throughout the day. A light/vrb flow pattern will mostly be in place for much of the day with winds becoming a bit more northwesterly later in the day.

KEY WATCHES/WARNINGS/ADVISORIES

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