We’ll take the heat up a notch for Thursday as even hotter air temperatures in the upper 90s — perhaps approaching 100° in a few spots — combine with dewpoints in the mid-to-upper 70s to produce heat indices pushing 110-113°. This potential has prompted an Extreme Heat Warning for Charleston and tidal Berkeley counties (Daniel Island, Hanahan) from 11am-8pm. Elsewhere in Berkeley and Dorchester counties, a Heat Advisory will be in effect for the same time period. In these areas, heat indices should peak in the 108-110° range — still quite dangerous, but not nearly as intense as what folks will see closer to the coast, where the moisture-rich maritime air will make it that much harder for your body to cool down. If you must be outside during the advisory/warning period tomorrow, take frequent breaks in the shade with plenty of water.
There will be a risk for a few showers and thunderstorms in the afternoon as some energy ripples by aloft, riding around the periphery of a strong ridge of high pressure centered in the midsection of the continental US. If storms can get going, a stray strong storm or two won’t be out of the question given plenty of moisture to work with. However, don’t count on a thunderstorm to impart much, if any, relief from the extreme heat.
It’s a very toasty start to the school year for Charleston County on Tuesday as this week’s heat wave will begin in earnest as high pressure aloft takes hold. We’ll start the day on a very mild note, with lows in the mid-to-upper 70s warming to the mid-90s in the afternoon. Dewpoints will run in the low-to-mid-70s inland, while closer to the coast, they’ll run in the upper 70s. That will help drive heat indices solidly into the 100s, with the highest heat indices expected in the Highway 17 corridor and points east. A Heat Advisory will be in effect for Charleston County and the southern part of Berkeley County from 11am-8pm, when heat indices should exceed 108° and could top out near 111° as the seabreeze pushes by. The aforementioned high pressure will make it much harder for thunderstorms to develop, though a couple popup showers will be possible. With that in mind, though, don’t count on thunderstorms to impart any relief from the heat.
Like the past few days, we will be getting our storms out of the way during Thursday’s morning and early afternoon hours as storms developing over the Atlantic drift coastward. Expect a warm and muggy start in the mid-70s, warming to around 90° in the afternoon once the sun emerges from behind the clouds. Showers and thunderstorms will once again be capable of producing heavy rain, with a flood advisory or two not out of the question especially if storms begin to train. We may also see a waterspout or two as well; earlier today, a storm off Kiawah produced four waterspouts (none of which made it to shore, at least). Keep an eye out on the beaches or if you have some boating planned.
What looks to be a top-five-warmest July on record will close on a slightly cooler and drier note as high pressure nudges in from the north. Thursday starts in the mid-70s across the area, warming to the low-to-mid-90s in the afternoon with plenty of sunshine. As mentioned, the drier air will keep heat indices a little more in check, though they may still get close to 100° near the coast where the more humid maritime airmass resides. But with all that in mind, it’ll still feel better outside than it did at the start of the week.
Tuesday looks similar to Monday, with temperatures warming into the low-to-mid-90s in the afternoon after another sultry start in the upper 70s to low 80s. Heat indices inland will run in the low 100s, but may push 108° as we get closer to the coast and the higher-dewpoint air. Southerly winds will continue to be breezy, with gusts pushing 30 MPH at times midday.
High pressure rebuilding aloft will bring more sunshine — but more heat, too. We’ll start Thursday in the mid-70s inland to upper 70s near the coast. From there, plenty of sunshine will drive highs into the mid-90s. Dewpoints will be fairly juicy — generally in the mid-to-upper 70s — and this will drive heat indices well into the mid-100s. Closer to the coast as well as in downtown, dewpoints near 80° will help drive the heat index up toward 108° for at least a brief period. Heat Advisory criteria is a heat index 108°-112° for two hours or more, and we certainly could be close in the coastal corridor. Regardless, be sure you’re taking frequent breaks in the shade with plenty of water if you’re working outside.
Showers and thunderstorms will feature prominently in the forecast on Tuesday as they develop around a stalled boundary lingering to the south. Periods of heavy rain will be possible, and an area or two of freshwater flooding can’t be totally ruled out. However, severe weather is unlikely, and this will largely be a beneficial rainfall event. Even better, highs should peak below 90° for the first time since June 24. So, even though there will be rain, it’ll be awfully nice to not be baking.
The main flooding concern arrives with the evening high tide; minor to moderate coastal flooding will be possible between 7-10 PM. We’ll need to monitor where the rain is carefully; any rain that coincides will cause issues downtown.
A slower frontal progression from the north will allow air temperatures to head back into the mid-to-upper 90s on Sunday, prompting another round of Heat Advisories and juicing up the atmosphere for another round of strong to potentially severe thunderstorms in the afternoon and evening.
It was a stifling hot Wednesday in the Lowcountry, with highs reaching the upper 90s and heat indices peaking between 113-116° in parts of the metro area. Another round of high heat is in store for Thursday, as temperatures once again return to the upper 90s. Dewpoints near the coast and behind the seabreeze should surge well into the mid-to-upper 70s once again, sending heat indices between 108-113° (with locally higher readings possible) in the Highway 17 corridor. This has prompted another Extreme Heat Warning for Charleston County as well as the southern portion of Berkeley County that includes Hanahan and Daniel Island. Elsewhere, a Heat Advisory will be in effect for heat indices around 108-110°. Model guidance still suggests a few showers and thunderstorms will fire off along and ahead of the seabreeze, which will help cool some of us off. Coastward storm motions moving against the inland-moving seabreeze could cause some back-building of thunderstorms with some locally heavy rain. The strongest storms could produce damaging wind gusts, and a warning or two can’t be totally ruled out as a result.
