July weather forecast
Reston, VA

July in Reston, Virginia, is a tropical summer month, with an average temperature fluctuating between 68.5°F (20.3°C) and 87.6°F (30.9°C).

Temperature

July is the warmest month, with an average high-temperature of 87.6°F (30.9°C) and an average low-temperature of 68.5°F (20.3°C).

Heat index

The average heat index in July is computed to be a very hot 98.6°F (37°C). Take special precautions - heat exhaustion and heat cramps are expected. Heatstroke may occur with lengthy activity.
Note that heat index values are valued for light wind and location in the shade. Exposure to direct sunshine can increase heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature', 'apparent temperature', 'real feel', or 'feels like', is what the temperature feels like to the human body when the air temperature is combined with the relative humidity. Additional factors like differences in body mass, height, and shape, wind, metabolic differences, and activity influence one's weather impression. Bear in mind that direct sunshine exposure increases weather impact, and may raise heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Children are often less aware of the need to rest and re-hydrate. Thirst is a late sign of dehydration - it is vital to remain hydrated, particularly during prolonged physical activities.
Perspiration is the human body's physiological response to high temperatures and is an attempt to lower body temperature through evaporation of sweat. Under high air temperature and humidity (high heat index) conditions, perspiration is limited, and the perception of heat is increased. If the body can not disperse the excessive heat and body temperature reaches conditions of hyperthermia, above 99.5°F (37.5°C) to 100.9°F (38.3°C), thermal conditions are potentially life-threatening.

Humidity

July is the least humid month in Reston, with an average relative humidity of 69%.

Rainfall

In Reston, during July, the rain falls for 15.1 days and regularly aggregates up to 2.68" (68mm) of precipitation. Throughout the year, in Reston, there are 152.8 rainfall days, and 27.64" (702mm) of precipitation is accumulated.

Snowfall

May through October are months without snowfall in Reston.

Daylight

In Reston, the average length of the day in July is 14h and 35min.
On the first day of July in Reston, sunrise is at 5:47 am and sunset at 8:39 pm. On the last day of the month, sunrise is at 6:09 am and sunset at 8:22 pm EDT.

Sunshine

The month with the most sunshine in Reston 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. A UV Index estimate of 6 to 7 represents a high health risk from unprotected exposure to Sun's UV rays for the ordinary person.
Note: In July, the average maximum UV index of 6 translate into the following recommendations:
Take precautions and adopt sun safety practices. Protection against sunburn is obliged. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects.