Naperville (IL) Temperature by Month
Naperville, Illinois, United States of America has an average annual maximum temperature of 15°C (59°F), ranging from -1°C (30°F) in January to 29°C (84°F) in July. Below you'll find a full monthly breakdown and a comparison with cities worldwide.
Naperville Monthly Temperatures
The weather in Naperville experiences significant differences between warm and cold seasons, with big shifts in temperature. At night, minimum temperatures range from 17°C (63°F) in July to -10°C (14°F) in January.
The chart below illustrates the average maximum day and minimum night temperatures in Naperville by month:
Temperatures tend to bottom out between 4 AM and 6 AM, then climb to their daily peak around 3 PM. July, the warmest month, sees 319 hours of sunshine.
The chart below shows the average temperature throughout the year:
Temperature: Naperville 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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Naperville vs World: Temperature Compared
Naperville's average annual maximum temperature is 15°C (59°F). To put that in context, here's how it compares to a few well-known destinations:
Lisbon, Portugal averages 21°C (70°F) annually — warm summers, mild winters, and rain mainly in the cooler months.
Interlaken, Switzerland averages 8°C (46°F) a year, with cold winters and cool summers thanks to its Alpine setting.
Chicago, USA averages 15°C (59°F) annually — known for extreme seasonal swings, from bitterly cold winters to warm summers.
Adelaide, Australia averages 21°C (70°F) a year, with warm summers, mild winters, and relatively low rainfall year-round.
What Does the Temperature Feel Like in Naperville?
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 Naperville, January is the coolest month, with average highs of -1°C (30°F) and humidity around 72% — considered high. In July, the warmest month, temperatures average 29°C (84°F) with 68% 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.
For cities and regions with significant elevation, altitude is one of the biggest factors shaping local temperatures. As a rule of thumb, temperatures fall by around 6°C for every 1,000 metres gained — so a city at 2,000 metres will typically be around 12°C cooler than a city at sea level in the same region. Higher ground also tends to see more dramatic day-to-night temperature swings, since thinner air loses heat faster after sunset.
For more on Naperville's weather — including monthly rainfall, sunshine hours, and humidity — visit our Naperville climate page.
