The week started with the state under high pressure, with light north-northeast winds and clear skies. Jocassee reported a morning low temperature of 46 degrees. Marine Corps Air Station Beaufort recorded a high temperature of 86 degrees. A decaying frontal boundary drifted over the Upstate late in the evening of May 7, triggering scattered rainshowers. The Greenville Downtown Airport reported 1.04 inches of rainfall. Rainshowers persisted into the morning of May 9. The Oconee County Airport reported 0.82 inches of rainfall. Ninety Nine Islands had a morning low temperature of 47 degrees. Orangeburg's high temperature on Tuesday reached 87 degrees.
High pressure continued to strengthen on Wednesday, May 9. Clear, dry conditions and light winds persisted on Wednesday. Lake Greenwood and Cedar Creek had a morning low temperature of 49 degrees. Orangeburg warmed to 88 degrees and Beaufort had a high temperature of 87 degrees. Jocassee started May 10 with low temperature of 47 degrees. The COOP observer at USC in Columbia reported a high temperature of 94 degrees. A weak upper-level trough passed over the state after sunset on May 10, triggering a few scattered rainshowers over the Upstate. Rock Hill reported 0.23 inches before midnight, Clemson and Florence received 0.11 inches. Table Rock reported 0.51 inches of rainfall on their 6 AM, May 11 report.
Jocassee had a morning low temperature of 49 degrees on Friday, May 10. High pressure shifted eastward on Friday, shifting surface winds to the west-northwest. High temperature date-records were tied at several observing sites and broken at sites listed below:
| May 11, 2018 (°F) | Previous Date-Record / Year (°F) |
|
|---|---|---|
| Orangeburg 2 | 98 | 95 / 2016 |
| Columbia Owens | 94 | 92 / 2017 |
| Edisto Middleton Plantation | 94 | 92 / 2017 |
| Orangeburg Airport | 93 | 92 / 2017 |
An isolated thunderstorm developed over Orangeburg County after 9 PM on May 11. The COOP observer in North reported a 1.23 inch rainfall from that thunderstorm. A CoCoRaHS observer, also in Orangeburg, reported a 1.47 inch rainfall total attributable to that same convective cell.
Saturday began with a low temperature of 53 degrees at Cedar Creek. Warming was rapid under clear skies. Columbia Metro Airport reported reaching a high temperature of 95 degrees. Again, several date-record temperatures were set:
| May 12, 2018 (°F) | Previous Date-Record / Year (°F) |
|
|---|---|---|
| Jamestown | 95 | 90 / 2017 |
| Cades 4W | 95 | 90 / 2016 |
| Florence Airport | 95 | 94 / 2000 |
| Holly Hill | 94 | 91 / 2017 |
On Saturday afternoon, a lee trough developed across the Midlands along the I-20 corridor triggering thunderstorms over Aiken, Lexington and Darlington counties. Darlington received 0.58 inches of heavy rain in less than one hour in a squall that also produced 35 mph sustained winds, and gusts to 58 mph.
Hot and dry conditions persisted on Sunday, May 13. Anderson had a morning low temperature of 57 degrees. Columbia Metro had a date-record high temperature of 98 degrees after a morning low of 67 degrees. Several other sites also reported date-record high temperatures:
| May 13, 2018 (°F) | Previous Date-Record / Year (°F) |
|
|---|---|---|
| Columbia Metro | 98 | 97 / 2000 |
| Pelion | 96 | 95 / 2000 |
| Lake City | 95 | 94 / 2000 |
| Holly Hill | 95 | 91 / 2015 |
(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 USC campus on May 12. This is South Carolina’s “second earliest” triple digit heat on record. The record earliest triple digit temperature known was on May 11, 1911 in Walterboro.
The lowest official temperature reported was 46 degrees at Jocassee and Ninety-Nine Islands on May 7.
The heaviest official 24-hour precipitation reported was 1.23 inches at North on May 12.
The state average precipitation for the seven-day period was 0.20 inches.
| Weekly* | Since Jan 1 | Departure | |
|---|---|---|---|
| Anderson Airport | 0.75 | 17.57 | 1.3 |
| Greer Airport | 0.65 | 18.18 | 0.9 |
| Charlotte, NC Airport | 0.23 | 15.07 | 0.0 |
| Columbia Metro Airport | 0.01 | 10.11 | -4.6 |
| Orangeburg Airport | 0.22 | 9.19 | -6.3 |
| Augusta, GA Airport | 0.00 | 10.34 | -5.5 |
| Florence Airport | 0.11 | 11.95 | -1.3 |
| North Myrtle Beach Airport | 0.00 | 13.04 | -2.3 |
| Charleston Air Force Base | 0.00 | 10.51 | -4.0 |
| Savannah, GA Airport | 0.00 | 8.38 | -6.0 |
| *Weekly precipitation totals ending midnight Sunday. |
4-inch depth soil temperature: Clinton: 69 degrees. Columbia: 73 degrees. Barnwell: 66 degrees. Mullins: 68 degrees.
Upstate river stages were below normal to normal.
Midlands and Pee Dee river stages were much below normal to normal.
Lowcountry river stages were much below normal to below normal.
Charleston Harbor (CHTS1): 75.9 degrees.
Capers Nearshore Buoy (Station 41029): 73.9 degrees.
