Weather in Herndon, VA
Herndon, Saturday, 8 August, 19:29
Overcast. Feels like 87°. High 88°, low 71°.
Monthly outlook for Herndon, VA: average high 83.4°, average low 66.5°. That is 0.6° below the climate normal for August. Precipitation is expected on 6 days (about 1.8 inches), against a normal of 6 days and 1.9 inches. The warmest day looks like 10 August (93.7°), the coolest 15 August (56.5°).
Ten-day blocks vs climate normal
| Period | Forecast high | Normal | Difference |
|---|---|---|---|
| 8 August – 17 August | 85.5° | 85.2° | +0.2° |
| 18 August – 27 August | 79.8° | 83.7° | -2.1° |
| 28 August – 6 September | at normal | 83° | — |
August records over 66 years
0
Herndon, Sunday, 9 August
Mostly clear. High 89°, low 71°.
0.12
Herndon, Monday, 10 August
Rain. High 94°, low 71°.
0.01Herndon, Tuesday, 11 August
Light rain. High 92°, low 69°.
0.02Herndon, Wednesday, 12 August
Light rain. High 87°, low 72°.
0.06Herndon, Thursday, 13 August
Light rain. High 89°, low 71°.
0.83Herndon, Friday, 14 August
Heavy rain. High 71°, low 61°.
0
Herndon, Saturday, 15 August
Clear. High 78°, low 56°.
0Herndon, Sunday, 16 August
Clear. High 79°, low 59°.
0Herndon, Monday, 17 August
Mostly clear. High 87°, low 63°.
0.3Herndon, Tuesday, 18 August
Rain. High 72°, low 69°.
0.01Herndon, Wednesday, 19 August
Light rain. High 86°, low 69°.
0Herndon, Thursday, 20 August
Overcast. High 84°, low 64°.
0.37Herndon, Friday, 21 August
Light rain. High 74°, low 68°.
0Herndon, Saturday, 22 August
Clear. High 87°, low 67°.
0Herndon, Sunday, 23 August
Overcast. High 77°, low 61°.
0.09
Herndon, Monday, 24 August
Climate normal for this date — 60-year average.
0.07Herndon, Tuesday, 25 August
Climate normal for this date — 60-year average.
0.04Herndon, Wednesday, 26 August
Climate normal for this date — 60-year average.
0.14
Herndon, Thursday, 27 August
Climate normal for this date — 60-year average.
0.15Herndon, Friday, 28 August
Climate normal for this date — 60-year average.
0.11Herndon, Saturday, 29 August
Climate normal for this date — 60-year average.
0.06Herndon, Sunday, 30 August
Climate normal for this date — 60-year average.
0.07Herndon, Monday, 31 August
Climate normal for this date — 60-year average.
0.11Herndon, Tuesday, 1 September
Climate normal for this date — 60-year average.
0.09Herndon, Wednesday, 2 September
Climate normal for this date — 60-year average.
0.09Herndon, Thursday, 3 September
Climate normal for this date — 60-year average.
0.1Herndon, Friday, 4 September
Climate normal for this date — 60-year average.
0.15Herndon, Saturday, 5 September
Climate normal for this date — 60-year average.
0.27Herndon, Sunday, 6 September
Climate normal for this date — 60-year average.
About the monthly outlook
How accurate is a 30-day forecast?
The first 16 days come from weather models — reliable for the first 3–5 days and progressively less so after that. Days 17 through 30 for Herndon, VA are built from the climate normal, the 60-year average, so they show typical weather for those dates rather than a specific forecast.
What does "above normal" mean?
We compare the forecast against the climate normal for those exact calendar days, computed from 60 years of observations. The deviation shows how much the coming month differs from a typical one.
Where do the 66-year records come from?
They are real temperature extremes recorded in Herndon, VA since 1960: the highest and lowest reading for each calendar date, with the year it happened.
How often is it updated?
The forecast portion refreshes every hour; the climate portion is based on long-term data and stays stable.
Sun and moon today
Weather history
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