July weather forecast
Herndon, VA

The peak of Herndon's summer arrives in July, bringing with it the highest temperatures of the year. July is the warmest month in Herndon, with the average high temperature reaching up to 87.8°F (31°C) and the low around 67.3°F (19.6°C). The warmth of July is complemented by clear blue skies and long daylight hours. These conditions make it an ideal time for a summer picnic or a swim in one of Herndon's pools. However, high humidity levels are also a part of the July weather package, making hydration a priority.

Temperature

In Herndon, the month of July is known for its highest average temperatures, reaching a high of 87.8°F (31°C) and a low of 67.3°F (19.6°C).

Heat index

The average heat index in July is computed to be a fiery hot 100.4°F (38°C). Ensure extra safety steps, heat exhaustion and heat cramps are likely. Long activity might lead to heatstroke.
Heat index's context suggests values are appropriate for shady areas and slight breezes. Uninterrupted exposure to the sun may boost the heat index values by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'felt air temperature', binds temperature metrics with humidity values to give a sense of the actual warmth. Metabolic differences, pregnancy status, and the level of physical activity are additional factors influencing an individual's weather perception. Always consider that direct sunlight exposure might heighten the heat's effects, pushing the heat index up by 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly important for children. Kids are usually in more danger than grown-ups as they tend to sweat less. Plus, their bigger skin surface in relation to their small frames and increased heat generation due to their activity level make them more susceptible.
Perspiring is the body's way of cooling down, particularly by allowing sweat to evaporate and take the heat with it. Elevated relative humidity disrupts typical body cooling by reducing the evaporation rate, consequently decreasing the body's cooling rate and enhancing the feeling of heat. When the body's heat gain surpasses its removal capacity, body temperature starts to climb, leading to potential heat-related ailments.

Humidity

July is the least humid month in Herndon, with an average relative humidity of 70%.

Rainfall

In Herndon, during July, the rain falls for 16.3 days and regularly aggregates up to 3.03" (77mm) of precipitation. In Herndon, during the entire year, the rain falls for 158.1 days and collects up to 31.46" (799mm) of precipitation.

Snowfall

In Herndon, snow does not fall in May through October.

Daylight

The average length of the day in July in Herndon is 14h and 35min.
On the first day of July in Herndon, sunrise is at 5:48 am and sunset at 8:39 pm. On the last day of the month, sunrise is at 6:10 am and sunset at 8:21 pm EDT.

Sunshine

The month with the most sunshine is July, with an average of 10.7h of sunshine.

UV index

May through August, with an average maximum UV index of 6, are months with the highest UV index in Herndon. A UV Index reading of 6 to 7 represents a high health risk from unsafe exposure to UV radiation for the ordinary person.
Note: The daily maximum UV index of 6 in July interprets into the following advice:
Stick with precautions and abide by sun safety procedures. Evading sunburn is essential. Limit your direct sun exposure, especially between 10 a.m. and 4 p.m., when UV radiation is strongest. Shade structures might not provide complete sun protection. Sunglasses providing both UVA and UVB protection are non-negotiable on sunlit days.