Upper-level high pressure provided enough subsidence to cause hot conditions on the 21st. Surface high pressure over the Atlantic caused moist air to move into the region from the south. The combination of the heat and humidity caused heat indices over 110 degrees in some locations.

Excessive Heat in KING GEORGE, VIRGINIA
From 21-JUL-11 13:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: Unknown

Heat indices were estimated to be in excess of 110 degrees based on observations nearby.

Excessive Heat in SOUTHERN FAUQUIER, VIRGINIA
From 21-JUL-11 13:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: Unknown

Heat indices were estimated to be in excess of 110 degrees based on observations nearby.

Heat in FREDERICK, VIRGINIA
From 21-JUL-11 15:00:00 to 21-JUL-11 18:00:00 (EST-5)
Reported by: AWOS

Heat indices up to 106 degrees were reported at Winchester.

Heat in WARREN, VIRGINIA
From 21-JUL-11 15:00:00 to 21-JUL-11 18:00:00 (EST-5)
Reported by: Unknown

Heat indices in excess of 105 degrees were estimated based on observations nearby.

Heat in CLARKE, VIRGINIA
From 21-JUL-11 15:00:00 to 21-JUL-11 18:00:00 (EST-5)
Reported by: Unknown

Heat indices in excess of 105 degrees were estimated based on observations nearby.

Heat in NELSON, VIRGINIA
From 21-JUL-11 15:00:00 to 21-JUL-11 18:00:00 (EST-5)
Reported by: Unknown

Heat indices in excess of 105 degrees were estimated based on observations nearby.

Heat in GREENE, VIRGINIA
From 21-JUL-11 15:00:00 to 21-JUL-11 18:00:00 (EST-5)
Reported by: Unknown

Heat indices in excess of 105 degrees were estimated based on observations nearby.

Heat in MADISON, VIRGINIA
From 21-JUL-11 14:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: Unknown

Heat indices in excess of 105 degrees were estimated based on observations nearby.

Heat in RAPPAHANNOCK, VIRGINIA
From 21-JUL-11 14:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: Unknown

Heat indices in excess of 105 degrees were estimated based on observations nearby.

Heat in ORANGE, VIRGINIA
From 21-JUL-11 15:00:00 to 21-JUL-11 18:00:00 (EST-5)
Reported by: Unknown

Heat indices in excess of 105 degrees were estimated based on observations nearby.

Heat in LOUDOUN, VIRGINIA
From 21-JUL-11 14:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: ASOS

Heat indices in excess of 105 degrees were reported at Dulles International Airport.

Heat in ALBEMARLE, VIRGINIA
From 21-JUL-11 15:00:00 to 21-JUL-11 18:00:00 (EST-5)
Reported by: ASOS

Heat indices in excess of 105 degrees were reported at the Charlottesville Airport.

Heat in NORTHERN FAUQUIER, VIRGINIA
From 21-JUL-11 14:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: Unknown

Heat indices in excess of 105 degrees were estimated based on observations nearby.

Excessive Heat in CULPEPER, VIRGINIA
From 21-JUL-11 13:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: AWOS

Heat indices up to 111 degrees were reported at Culpeper.

Excessive Heat in PRINCE WILLIAM, VIRGINIA
From 21-JUL-11 13:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: AWOS

Heat indices up to 112 degrees were reported at Quantico.

Excessive Heat in FAIRFAX, VIRGINIA
From 21-JUL-11 13:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: AWOS

Heat indices up to 110 degrees were reported at Fort Belvoir.

Excessive Heat in STAFFORD, VIRGINIA
From 21-JUL-11 13:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: Unknown

Heat indices were estimated to be in excess of 110 degrees based on observations nearby.

Excessive Heat in SPOTSYLVANIA, VIRGINIA
From 21-JUL-11 13:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: Unknown

Heat indices were estimated to be in excess of 110 degrees based on observations nearby.

Excessive Heat in ARLINGTON, VIRGINIA
From 21-JUL-11 14:00:00 to 21-JUL-11 17:00:00 (EST-5)
Reported by: ASOS

Heat indices up to 112 degrees were reported at Reagan National.