A southerly flow of humid tropical air persisted over the state during the entire week. Subtropical Storm Alberto formed over the eastern Gulf of Mexico and made landfall along the coast of the Florida Panhandle on Monday, May 28. A surface trough extended northeast from Alberto triggering heavy rain and strong thunderstorms. An EF-0 tornado with estimated 80 mph winds touched down near Cameron in Calhoun County. The tornado was 150 yards wide and on the ground for 0.29 miles, damaging trees, roofs and fences. Jocassee and Caesars Head began the week with a morning low temperature of 62 degrees. Aiken reported a high temperature of 87 degrees. North Myrtle Beach reported a 2.75 inch rainfall total. Jocassee reported a 24-hour rainfall total of 3.80 inches on their 7 AM observation, submitted on May 29.
Jocassee's morning low temperature on May 29 was 64 degrees as Alberto tracked west of the state. Columbia and Florence had a high temperature of 89 degrees. A stationary frontal boundary over the state triggered more rain and thunderstorms. The Greenville-Spartanburg Airport received 1.76 inches of rainfall. On May 30, Florence had a high temperature of 90 degrees after a morning low temperature of 75 degrees. Diurnal heating forced scattered afternoon rainshowers and thunderstorms in the moist airmass over the state. Anderson's rainfall totaled 0.88 inches and Charleston's rainfall was 0.20 inches.
May 31 began with a morning low temperature of 63 degrees at Jocassee. The Columbia area warmed to 89 degrees. Charleston received 1.55 inches of rain for a new May rainfall record of 10.62 inches, beating the previous monthly record of 9.28 inches set in 1957. The May state rainfall record of 17.65 inches, set in Long Creek in 1976, was exceeded by the May 2018 rainfall totals at Hogback Mountain (18.90 inches), Sassafras Mountain (19.03 inches), and Slicking Mountain (23.19 inches). The May 2018 rainfall range held a maximum at Slicking Mountain with 23.19 inches, and the minimum amount of rainfall measured was at Columbia Metro Airport with 2.76 inches.
Hot and humid conditions with afternoon convection continued on the first day of June. USC and the Witherbee RAWS station recorded a high temperature of 94 degrees. Anderson reported 1.36 inches of rainfall from an evening thunderstorm. On June 2 Walhalla had a morning low temperature of 62 degrees. USC reported an afternoon high temperature of 95 degrees. 0.83 inches of rain fell at the Charleston Airport. On June 3, USC closed out the week with a morning low temperature of 72 degrees and an afternoon high temperature of 96 degrees. Pre-frontal thunderstorms before midnight on June 3 produced dime to quarter size hail over Red Bank and South Congaree in Lexington County.
(Note: The highest and lowest official temperatures and highest precipitation totals provided below are based on observations from the National Weather Service Cooperative Observer network and the National Weather Service's Forecast Offices.)
The highest official temperature reported was 97 degrees at Georgetown on June 3.
The lowest official temperature reported was 60 degrees at Jocassee on June 1.
The heaviest official 24-hour precipitation reported was 6.28 inches on Hogback Mountain on May 29.
The state average precipitation for the seven-day period was 1.70 inches.
| Weekly* | Since Jan 1 | Departure | |
|---|---|---|---|
| Anderson Airport | 4.25 | 26.32 | 7.4 |
| Greenville-Spartanburg Airport | 3.31 | 24.77 | 5.0 |
| Charlotte, NC Airport | 1.75 | 18.53 | 1.2 |
| Columbia Metro Airport | 0.65 | 12.88 | -4.0 |
| Orangeburg Airport | 1.54 | 16.76 | -1.3 |
| Augusta, GA Airport | 2.80 | 18.96 | 1.0 |
| Florence Airport | 1.77 | 16.42 | 0.6 |
| North Myrtle Beach Airport | 3.02 | 18.54 | 0.7 |
| Charleston Airport | 3.06 | 21.96 | 5.2 |
| Savannah, GA Airport | 2.37 | 15.42 | -1.4 |
| *Weekly precipitation totals ending midnight Sunday. |
4-inch depth soil temperature: Clinton: 73 degrees. Columbia: 78 degrees. Barnwell: 71 degrees. Mullins: 72 degrees.
Upstate river stages were normal to much above normal.
Midlands and Pee Dee river stages were normal to much above normal.
Lowcountry river stages were above normal to much above normal.
Charleston Harbor (CHTS1): 81.3 degrees.
Capers Nearshore Buoy (Station 41029): 79.5 degrees.
