On Monday, the center of Tropical Storm Irma passed 200 miles southwest of the state. The storm's expansive eastern rain and precipitation shield affected the entire state with periods of heavy rain and damaging tropical storm force winds on Monday and early Tuesday. The strongest winds and heaviest rainfall amounts were reported along the coast and with widespread flooding due to storm surge, heavy surf, King tides and persistent easterly winds. The Charleston Air Force Base had the highest official maximum sustained wind of 37 knots or 43 miles per hour. The Beaufort Marine Corps Air Station had a peak gust of 61 mph. The 10 meter high Folly Beach C-MAN site recorded 51 mph east winds gusting to 64 mph. A nearby non-NWS WeatherFlow instrument captured a gust of 72.5 mph. The Hilton Head Airport had a minimum sea level pressure of 999.7 millibars.
Strong winds blew down hundreds of trees across Beaufort, Charleston, Colleton, Dorchester, Hampton and Jasper counties that blocked roads and knocked out power lines. A weak, short-lived EF0 tornado touched down between Sullivan's Island and Mount Pleasant. The tornado was only 90 yards wide and on the ground for 0.57 miles. Tornadic damage was confined to numerous downed tree limbs, uprooted trees and minor property damage.
The peak storm surge in Charleston was 4.87 feet and the peak storm tide was 9.92 feet above mean lower low water (MLLW). The storm tide was over four feet above normal and one of the highest surges since 1989's Hurricane Hugo. Many streets were flooded and impassable in Charleston. Dramatic images showed water cascading over the Battery and filling lower Charleston Peninsula streets to waist level.
Irma's outer rain bands dropped heavy rain along the coast that exacerbated storm surge and coastal surf flooding. During a period from 8:00 p.m. September 9 through 2 A.M. September 13, the Church Creek gage near West Ashley collected 8.97 inches of rainfall. 8.22 inches was collected inland at Youman's Farm in Hampton County during the same period. 6.26 inches or rain was reported by the Beaufort Marine Corp Air Station. A CoCoRaHS observer in Beaufort reported 9.07 inches of rain.
Conditions were less dire in Georgetown and Horry counties. The Myrtle Beach International Airport reported a peak wind gust of 54 mph and a 24-hour rainfall amount of 2.91 inches. The Georgetown County Airport had a peak gust of 61 mph from the northeast but a 24-hour rainfall total of 4.33 inches. Storm surge along the coast in Horry County was estimated to be 2.5 feet.
Away from the coast, the Holly Hill 1 SW COOP observer collected 6.57 inches of rain in 24 hours. Across the Midlands rainfall amounts of 4.11 inches, 3.78 inches, and 2.52 inches were recorded at the Augusta Bush Airfield in Georgia, the Columbia Metro Airport, and the Florence Regional Airport respectively. The Clemson-Oconee County Airport had the highest inland gust of 57.5 mph. The Columbia Metro Airport had a 51 mph observation.
The maximum temperature during Monday's tropical storm event was 78 degrees observed both at the North Myrtle Beach Airport and the Charleston Air Force Base. Monday's low temperature was 47 degrees on Sassafras Mountain.
Clearing was rapid Tuesday afternoon after a lingering morning overcast. Tuesday's high temperature rose to 86 degrees at the Dillon COOP site. With Irma's remnant circulation well to the northwest, high pressure built in Wednesday bringing cooler, drier air. Wednesday morning's low temperature was 53 degrees at Lake Greenwood under clear skies. The Columbia Metro Airport had a Wednesday high temperature of 86 degrees with southerly winds.
Late night rain showers developed late night Wednesday over the Upstate and Midlands. 0.54 inches of rain fell at the Wateree Dam. Overcast conditions persisted for half the day on Thursday as the southern extent of Irma's remnant cloud shield drifted over the state. Afternoon clearing allowed temperatures to warm to 90 degrees at the Jamestown COOP site.
High pressure settled in over the state on Friday and dominated the state's weather through Sunday. The weekend remained rain-free. The weekend low temperature was 56 degrees Friday Morning at Table Rock. 92 degrees was on Friday's high temperature at the Orangeburg 2 COOP site.
(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 92 degrees Orangeburg 2 on September 15.
The lowest official temperature reported was 47 degrees on Sassafras Mountain on September 11.
The heaviest official 24-hour rainfall reported was 6.57 inches at Holly Hill 1 SW on September 12.
The state average rainfall for the seven-day period was 3.2 inches.
| Weekly | Jan 1 | Departure | |
|---|---|---|---|
| Anderson Airport | 1.84 | 42.16 | 10.4 |
| Greer Airport | 2.42 | 42.11 | 7.6 |
| Charlotte, NC Airport | 1.14 | 37.68 | 7.3 |
| Columbia Metro Airport | 3.79 | 40.86 | 6.8 |
| Orangeburg Airport | 3.86 | 32.32 | -3.2 |
| Augusta, GA Airport | 4.11 | 38.66 | 6.0 |
| Florence Airport | 2.56 | 35.62 | 3.0 |
| North Myrtle Beach Airport | 1.97 | 39.87 | 0.6 |
| Charleston Air Force Base | 5.51 | 45.10 | 5.6 |
| Savannah, GA Airport | 4.74 | 47.49 | 10.3 |
Weekly rainfall totals ending midnight Sunday.
4-inch depth soil temperature: Clinton 74 degrees. Columbia 77 degrees. Barnwell 70 degrees. Mullins 69 degrees
Most South Carolina river stages were normal to above normal.
Charleston Harbor water temperature: 79 degrees.
Capers Nearshore Buoy (Station 41029): 80 degrees.
