The 24-hour rainfall totals for the Charleston area, ending Monday morning, October 5, ranged from two to four inches, with some downtown locations reporting more than six inches. A strong wedge of high pressure built into the area on Monday and continued into Tuesday as a low-pressure system developed off the Georgia coast. These gusty northeast winds contributed to hazardous marine conditions in nearshore and offshore zones, dangerous rip currents, and coastal flooding, and persisted into Wednesday. The Charleston Harbor Tidal gauge recorded peak tides between 7.21 ft and 7.46 ft MLLW on Tuesday and Wednesday, causing saltwater flooding in downtown Charleston and other low-lying coastal areas.
On Wednesday, October 7, Tropical Storm Isaias formed in the Gulf during the mid-morning and quickly strengthened into a hurricane by Wednesday evening. High pressure continued over the region, with dry conditions and cooler morning temperatures, with lows in the 50s and highs in the upper 70s to mid-80s on Wednesday and Thursday.
Hurricane Isaias became a major hurricane with sustained winds of 120 mph on Friday morning and would affect weather across the state for the rest of the period. On Friday, Hurricane Isaias made landfall near Destin, FL, as a Cat 2 hurricane with sustained winds of 105 mph late Friday evening. By Saturday morning, the storm was designated post-tropical as rain overspread the area, and much of the state was under a Flood Watch through Sunday morning. Strong winds and saturated soil brought down trees in parts of Oconee County. The morning high tide at the Charleston Harbor tidal gauge crested at 7.76 ft MLLW; rainfall during the high tides contributed to coastal flooding. A warm front moved northward across the state Saturday afternoon, bringing higher rainfall rates in some rainbands and embedded severe thunderstorms. Heavy rain was observed across parts of the Upstate and Midlands, with flash flooding reported in Aiken, Saluda, and Lexington counties Saturday afternoon into the evening. Survey teams with the National Weather Service confirmed one EF2 tornado in Barwell County, two EF1 tornadoes in Allendale County, an EF1 tornado in Aiken County, and an EF1 tornado in Barnwell County from Saturday's storms. Another line of strong storms, associated with a cold front, moved through the state on Sunday morning and afternoon. Some of the thunderstorms were severe, and one storm produced an EF2 tornado in Newberry County. Behind the front, drier and cooler air pushed into the region.
(Note: The highest and lowest official temperatures and highest precipitation totals provided below are based on observations from the National Weather Service (NWS) Cooperative Observer network and the National Weather Service's Forecast Offices.)| Weekly* | Since Jan 1 | Departure | |
|---|---|---|---|
| Anderson Airport | 2.41 | 26.43 | -10.0 |
| Greer Airport | 3.23 | 33.87 | -5.2 |
| Charlotte, NC Airport | 2.63 | 28.06 | -6.8 |
| Columbia Metro Airport | 1.29 | 23.41 | -13.6 |
| Orangeburg 2 (COOP) | 1.15 | 26.16 | -15.5 |
| Augusta, GA Airport | 2.64 | 30.17 | -5.9 |
| Florence Airport | 0.91 | 29.50 | -7.8 |
| North Myrtle Beach Airport | 1.24 | 22.39 | -17.2 | Charleston Air Force Base | 1.73 | 27.9 | -16.2 |
| Savannah, GA Airport | 0.82 | 24.27 | -16.2 |
| *Weekly precipitation totals ending midnight Sunday. M - denotes total with missing values. s - denotes total with suspect data. |
4-inch depth soil temperature: Columbia: 71 degrees. Barnwell: 67 degrees. Mullins: 68 degrees.
Most of the state received at least half an inch of rain during the period, with most of the rainfall reported over the weekend in association with the remnants of Hurricane Isaias. Rainfall totals ranged from half an inch in portions of Bamberg, Chesterfield, Dillon, Hampton, Jasper, and Orangeburg counties to over four inches in parts of Aiken, Cherokee, Edgefield, Greenville, Newberry, Saluda, Spartanburg, and Union counties.
With several periods of rainfall across the state, the U.S. Drought Monitor map released on Thursday, October 6, showed continued improvement to moderate (D1) conditions in parts of the northern Midlands, as well as the removal of extreme (D3) drought conditions in Colleton and Hampton counties in the Lowcountry and in Florence, Georgetown, Horry, Marion, and Williamsburg counties in the Pee Dee. Despite some rainfall during the current and previous periods, severe (D2) drought conditions persisted across portions of the Coastal Plain, while D1 and abnormally dry (D0) conditions remained statewide.
During the period, elevated tidal gauge heights caused minor to moderate coastal flooding in low-lying areas. Heavy rain over the weekend caused a few small tributaries in the Upstate to reach action stage, while most main-stem rivers saw increased river heights. The Broad River at Alston and the Congaree River at Columbia rose to action stage, while the Congaree River at Carolina Eastman reached minor flood stage. The 14-day average streamflow values are no longer available because some USGS products have been decommissioned. Current streamflow information is available at https://waterdata.usgs.gov/state/South%20Carolina/.
