Average Sunshine in Illinois for December

Number of Sunny Days

In the table below, the average number of Sunny Days for a city in Illinois is the total days this month when the sky is mostly clear. This includes the days when cloud covers up to 30% of the sky during daylight hours.

Partly Sunny Days have cloud covering from 40% to 70% of the sky during the daytime.

Total Days With Sun is a sum of the Sunny plus Partly Sunny days. The rest of the days are mainly overcast, with at least 80% cloud cover. All the numbers are annual averages, made from years of weather watching.

Amount of Sun

Here's another way to look at how much sunshine a city gets. The % Sun number measures the percentage of time between sunrise and sunset that sunshine reaches the ground. Again, these amounts are monthly averages based on many years of weather observations.