Herndon Temperature by Month
The average annual maximum temperature in Herndon, Virginia, United States of America is 19°C (66°F), with daytime highs ranging from 6°C (43°F) in January to 31°C (88°F) in July. This page covers monthly averages, day-night differences, and how Herndon compares to cities worldwide.
Herndon Monthly Temperatures
The climate in Herndon is dynamic, ranging widely from chilly in winter to very warm in summer. Nights are significantly colder, with lows dropping from 20°C (68°F) in July to -4°C (25°F) in January.
The chart below illustrates the average maximum day and minimum night temperatures in Herndon by month:
The coolest part of the day is typically between 4 AM and 6 AM, while 3 PM is usually the warmest, when solar heating is at its peak. July, the city's warmest month, averages 279 hours of sunshine.
The chart below shows the average temperature throughout the year:
Temperature: Herndon vs the United States of America
The map below shows the annual temperature across the United States of America. You can also select individual months if you want to compare a specific time of year.
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Herndon vs World: Temperature Compared
Herndon's average annual maximum temperature is 19°C (66°F). To put that in context, here's how it compares to a few well-known destinations:
Seville, Spain averages 23°C (73°F) a year — one of the warmer cities in Western Europe, with long hot summers.
Interlaken, Switzerland averages 8°C (46°F) a year, with cold winters and cool summers thanks to its Alpine setting.
Osaka, Japan averages 22°C (72°F) annually, with hot humid summers, mild winters, and pleasant spring and autumn seasons.
Brisbane, Australia averages 26°C (79°F) a year, with warm winters and hot, humid summers.
What Does the Temperature Feel Like in Herndon?
Temperature alone doesn't tell the whole story — humidity plays a big role in how warm or cold it actually feels. High humidity in summer makes the heat feel more intense, particularly once temperatures climb above 25°C. In winter, the same humidity can make cold air feel sharper than the thermometer suggests.
In the cooler months, when temperatures drop below 10°C, high humidity makes the cold feel more cutting than it would in dry conditions.
In Herndon, January is the coolest month, with average highs of 6°C (43°F) and humidity around 62% — considered high. In July, the warmest month, temperatures average 31°C (88°F) with 67% humidity — conditions that feel high. For a full picture, see our humidity page.
Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.
The readings come from a range of sources — land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.
Seasonal temperature shifts influence more than just how warm it feels — they also drive changes in rainfall, cloud cover, and wind patterns throughout the year.
Warmer air holds more moisture, which tends to mean heavier or more frequent rain during the warmer months. When temperatures drop in winter, any precipitation that does fall is more likely to come as snow or sleet, though in Herndon this rarely lasts long on the ground.
For more on Herndon's weather — including monthly rainfall, sunshine hours, and humidity — visit our Herndon climate page.
