The week started off with a weak surface trough over the area, which led to southerly flow and increased the amount of moisture in the atmosphere. Thunderstorms developed late on Monday, July 16, and because of light winds were slow to move, causing locally heavy rainfall along the Georgia and South Carolina border. Many CoCoRaHS stations in Aiken County reported over 3 inches of rain, with some totals closer to 6 inches, and in Beaufort County, the CoCoRaHS observers submitted reports of up to 4 inches of rain from the storms. The National Weather Service (NWS) Station in Long Creek tied a record high minimum temperature of 70 degrees, that was set back on the same date in 1970. The unsettled pattern continued on July 17 as a surface front moved across the Upstate, causing thunderstorms to develop. Multiple reports were received of a large number of trees being blown down in Greenville and Anderson counties. An NWS employee measured 2.41 inches of rain, and many reports came in from the Sumter area of ponding water on several flood-prone roads. Temperatures in the mid 90’s were observed across much of the state, except the typically cooler places in the Upstate.
The front became stationary over the Central Savannah River Area on Wednesday, July 18, and produced afternoon and evening thunderstorms across east central Georgia and coastal South Carolina. Lightning struck a power pole on Folly Beach Road resulting in a power outage on Folly Beach. Pea-sized hail was reported in Goose Creek and Cainhoy, and wind associated with the thunderstorms caused tree damage in Grays. While some areas experienced rainfall and cooler temperatures, most of the Midlands had highs in the mid-to-upper 90’s with very little rain, which led to reports of dry conditions across the region. The following day, July 19, a wave of low pressure moved along the front, triggering heavy rain. Four CoCoRaHS stations in Beaufort County reported over 2 inches of rain, and law enforcement officials noted that some area roads were impassable due to over a foot of standing water. CoCoRaHS station Summerville 1.7 W (SC-DC-53) reported 3.56 inches of rain.
Training thunderstorms during the morning hours on Friday, July 20 produced heavy rains over the course of a few hours along the southeastern coast. The freshwater flooding in downtown Charleston closed many residential streets, including major roads such as Highway 17. Multiple reports of stranded motorists and water waist high in some locations of Charleston prompted law enforcement officials to encourage people to stay away from downtown. The heaviest rains were confined closer to the coast. Two downtown CoCoRaHS stations reported over 8 inches (8.76 inches at 2 S North Charleston and 8.37 inches at 2 SW Daniel Island), with many more over 6 inches. Further inland, the Charleston International Airport measured 1.25 inches, and the National Weather Service Office in Charleston received 2.45 inches at their location. Additional heavy rains fell over portions of Horry and Georgetown counties with rainfall totals up to 6 inches in some locations. The rains helped keep maximum temperatures cool in the region, with the stations in North Myrtle Beach, McClellanville, and Georgetown reporting high temperatures of the day below 80 degrees.
High pressure weakened over the Upstate as a cold front, associated with the low-pressure system that caused severe weather in the Midwest, worked its way toward the area on July 21. Severe thunderstorms developed in the Upstate and reports of downed trees and power lines were made in Abbeville, Anderson, Cherokee, Greenwood, Oconee, and Spartanburg counties. The storm damage in Anderson County from was straight-line winds, and the NWS survey of an area south of Belton between Honea Path and Antreville estimated wind speeds of around 85 mph. Multiple reports of hail, between the size of a quarter (1.00 inches) and golf ball-sized (1.75 inches), were made in Anderson, Oconee, and Spartanburg. Pea to nickel-sized hail was reported in the Midlands as the storms pushed through the area overnight Saturday into Sunday morning. On Sunday, July 22, the cold front became stalled over the Midlands and produced thunderstorms over portions of the Lowcountry and Pee Dee regions. Strong storms produced pea-sized hail in Cainhoy, and the automated station at the Mount Pleasant Airport reported a wind gust of 41 mph. The high temperature of 85 degrees at Greenville-Spartanburg Airport was 5 degrees below the long-term average maximum temperature of the date.
(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 100 degrees at Columbia USC Campus on July 18.
The lowest official temperature reported was 60 degrees at Walhalla July 21.
The heaviest official 24-hour precipitation reported was 4.86 inches at the National Weather Service Cooperative station at the Edisto Island Middleton Plantation ending at midnight on July 20.
The state average precipitation for the seven-day period was 2.00 inches.
Darlington observed no measurable rain during the week, and for July 1-22, 2018 has received less than 15 percent of its average, only 0.51 inches, for the month.
| Weekly* | Since Jan 1 | Departure | |
|---|---|---|---|
| Anderson Airport | 3.81 | 35.64 | 10.9 |
| Greer Airport | 0.82 | 30.85 | 4.3 |
| Charlotte, NC Airport | 0.91 | 22.94 | -0.3 |
| Columbia Metro Airport | 0.16 | 16.82 | -8.1 |
| Orangeburg Airport | 2.22 | 23.00 | -3.7 |
| Augusta, GA Airport | 1.13 | 25.76 | 0.5 |
| Florence Airport | 0.35 | 23.60 | 0.0 |
| North Myrtle Beach Airport | 5.87 | 29.74 | 3.5 |
| Charleston Air Force Base | 2.34 | 29.83 | 3.2 |
| Savannah, GA Airport | 2.01 | 21.07 | -6.7 |
| *Weekly precipitation totals ending midnight Sunday. |
4-inch depth soil temperature: Clinton: 77 degrees. Columbia: 82 degrees. Barnwell: 75 degrees. Mullins: 74 degrees.
Rainfall was more widespread over the state last week, improving rivers levels in some locations of the Upstate and Low Country. Despite the broader coverage in precipitation, areas in the north Midlands and Pee Dee regions received less than an inch and stream flows in the Edisto River near Orangeburg, Black Creek at Hartsville and McBee, and the Little Pee Dee near Galivants Ferry were reporting below normal streamflow.
Charleston Harbor (CHTS1): 85.6 degrees.
Capers Nearshore Buoy (Station 41029): 84.6 degrees.
Fripps Nearshore Buoy (Station 41033): 85.3 degrees.
