Another extremely hot day is on tap for Tuesday as temperatures take what should be one last shot at the 100° mark before sanity begins a slow return to the forecast. We’ll start the day near 80° inland of the coast, and we’re almost assuredly not getting below 80° at the coast and in downtown Charleston. From there, temperatures will soar into the upper 90s to near 100°, with the best risk of reaching the 100° mark inland of Highway 17. And then there are the dewpoints running in the mid-to-upper 70s, which will propel heat indices well into the mid-110s for many of us, with a few readings getting uncomfortably close to 120° in more rural spots. For the first time in this heat wave, an Extreme Heat Warning is in effect for the entire Tri-County, including Dorchester; to this point, we’ve only seen those warnings come out for Berkeley and Charleston. Continue to heed precautions for extreme heat: air conditioning if at all possible, but frequent breaks in the shade with water if you must be outdoors.
There will be a slightly better chance of thunderstorms Tuesday afternoon than we saw on Monday, which will cool some of us off. The price for this, though, is an elevated risk for strong and potentially damaging wind gusts, excessive lightning, and very heavy — perhaps flooding — rain in a few spots. Instability will be running on the high end of what we usually see around these parts, so any storm that can take advantage could take off like a rocket. The good news is that without much shear, storms will generally pop, rain for a while, and then collapse.
Extreme Heat Warnings look to take a break on Sunday, but that is little solace with heat indices expected to continue to peak into the lower 110s in the afternoon, well into Heat Advisory criteria. Scattered showers and thunderstorms should develop again in the afternoon along the seabreeze, and a few of those could be on the strong side given plenty of instability once again. We’ll also see a risk for flooding, especially where storms train in the same areas, courtesy of a well-saturated atmosphere. Be ready for conditions to change quickly, particularly after 3-4 PM.
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.
