Saint Charles (IL) Temperature by Month
Saint Charles in Illinois, United States of America sees significant seasonal temperature differences, with daytime highs between -1°C (30°F) in January and 29°C (84°F) in July, averaging 15°C (59°F) annually. Explore the full monthly breakdown below.
Saint Charles Monthly Temperatures
In Saint Charles, temperatures can shift dramatically between warm in summer and very cold in winter. Nights follow the same pattern, with lows ranging 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 Saint Charles by month:
Low temperatures are most often recorded between 4 AM and 6 AM, while highs typically occur around 3 PM. July, the city's warmest month, sees 319 hours of sunshine.
The chart below shows the average temperature throughout the year:
Temperature: Saint Charles 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.
very warm
warm
pleasant
moderate
cold
very cold
Saint Charles vs World: Temperature Compared
Saint Charles'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:
Rome, Italy averages 20°C (68°F) annually, with reliably warm summers and comfortable winters.
Toronto, Canada averages 13°C (55°F) annually, with cold snowy winters balanced by genuinely warm summers.
Seoul, South Korea averages 18°C (64°F) a year, with four clear seasons, cold winters, and hot humid summers.
Melbourne, Australia averages 20°C (68°F) annually — known for unpredictable weather, with four seasons sometimes happening in one day.
What Does the Temperature Feel Like in Saint Charles?
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 Saint Charles, 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 Saint Charles's weather — including monthly rainfall, sunshine hours, and humidity — visit our Saint Charles climate page.
