Freeport (IL) Temperature by Month

The average annual maximum temperature in Freeport, Illinois, United States of America is 14°C (57°F), with daytime highs ranging from -2°C (28°F) in January to 28°C (82°F) in July. This page covers monthly averages, day-night differences, and how Freeport compares to cities worldwide.

Visitors to Freeport can expect significant temperature changes throughout the year. Nighttime temperatures also vary widely, ranging from 17°C (63°F) in July to -12°C (10°F) in January.

The chart below illustrates the average maximum day and minimum night temperatures in Freeport by month:

From around 4 AM to 6 AM temperatures are at their lowest; by 3 PM they've climbed to their daily peak. July, the warmest month, averages 301 hours of sunshine.

The chart below shows the average temperature throughout the year:

Freeport's average annual maximum temperature is 14°C (57°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.

On the cooler end, Oslo, Norway averages just 10°C (50°F) annually, with pleasant summers but long, cold winters.

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.

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 Freeport this rarely lasts long on the ground.

For more on Freeport's weather, including monthly rainfall, sunshine hours, and humidity, visit our Freeport climate page.