| Point Forecast: Herndon VA 38.97N 77.38W (Elev. 354 ft) |
Last Update: 1:30 am EDT Jul 20, 2025 |
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| Date | 07/20 | 07/21 | ||||||||||||||||||||||
| Hour (EDT) | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 00 | 01 | 02 |
| Temperature (°F) | 74 | 73 | 73 | 73 | 73 | 76 | 79 | 82 | 83 | 85 | 87 | 88 | 88 | 89 | 88 | 88 | 86 | 84 | 81 | 80 | 79 | 78 | 77 | 76 |
| Dewpoint (°F) | 73 | 73 | 73 | 72 | 73 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 74 | 74 | 73 | 73 | 72 | 72 | 72 | 72 | 71 | 71 | 70 |
| Heat Index (°F) | 76 | 79 | 89 | 90 | 94 | 96 | 98 | 98 | 98 | 97 | 96 | 93 | 90 | 85 | 84 | 79 | 78 | 77 | 76 | |||||
| Surface Wind (mph) | 2 | 2 | 2 | 2 | 2 | 3 | 5 | 6 | 8 | 9 | 9 | 10 | 10 | 10 | 10 | 10 | 9 | 8 | 8 | 8 | 8 | 8 | 7 | 7 |
| Wind Dir | S | SW | SW | SW | SW | W | W | W | W | W | W | W | W | W | W | W | W | W | NW | NW | NW | NW | NW | NW |
| Gust | 18 | 18 | 18 | |||||||||||||||||||||
| Sky Cover (%) | 41 | 39 | 62 | 54 | 55 | 52 | 35 | 42 | 46 | 50 | 51 | 53 | 44 | 32 | 28 | 25 | 22 | 31 | 25 | 30 | 26 | 37 | 51 | 46 |
| Precipitation Potential (%) | 3 | 3 | 3 | 3 | 4 | 4 | 3 | 6 | 12 | 10 | 13 | 18 | 15 | 12 | 11 | 13 | 13 | 8 | 7 | 6 | 6 | 6 | 6 | 4 |
| Relative Humidity (%) | 97 | 100 | 100 | 97 | 100 | 97 | 88 | 79 | 77 | 72 | 68 | 66 | 66 | 61 | 63 | 61 | 65 | 67 | 74 | 77 | 79 | 79 | 82 | 82 |
| Rain | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | SChc | SChc | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Thunder | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | SChc | SChc | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Date | 07/22 | |||||||||||||||||||||||
| Hour (EDT) | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 00 | 01 | 02 |
| Temperature (°F) | 75 | 73 | 73 | 72 | 72 | 73 | 76 | 77 | 78 | 80 | 82 | 83 | 84 | 84 | 83 | 82 | 81 | 79 | 77 | 74 | 72 | 70 | 69 | 68 |
| Dewpoint (°F) | 70 | 69 | 69 | 68 | 68 | 69 | 68 | 67 | 67 | 66 | 66 | 65 | 64 | 64 | 63 | 63 | 63 | 63 | 63 | 63 | 62 | 61 | 60 | 59 |
| Heat Index (°F) | 75 | 76 | 77 | 78 | 82 | 84 | 85 | 85 | 85 | 84 | 83 | 82 | 79 | 77 | ||||||||||
| Surface Wind (mph) | 7 | 6 | 6 | 6 | 6 | 6 | 6 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 6 | 6 | 5 | 3 | 3 | 3 | 3 | 5 | 5 |
| Wind Dir | NW | NW | NW | N | N | N | N | N | N | N | N | N | N | N | N | N | N | NE | NE | NE | NE | NE | NE | NE |
| Gust | ||||||||||||||||||||||||
| Sky Cover (%) | 53 | 40 | 48 | 57 | 46 | 52 | 60 | 58 | 55 | 46 | 38 | 29 | 28 | 26 | 25 | 26 | 27 | 28 | 26 | 25 | 23 | 21 | 18 | 16 |
| Precipitation Potential (%) | 4 | 4 | 4 | 4 | 8 | 6 | 6 | 6 | 6 | 6 | 6 | 10 | 10 | 10 | 10 | 10 | 10 | 6 | 6 | 6 | 6 | 6 | 6 | 4 |
| Relative Humidity (%) | 84 | 87 | 87 | 87 | 87 | 87 | 76 | 71 | 69 | 62 | 58 | 55 | 51 | 51 | 51 | 53 | 54 | 58 | 62 | 69 | 71 | 73 | 73 | 73 |
| Rain | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Thunder | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
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