Brace yourself. Tonight could be one of the coldest of the week. But Saturday night is also in the running for the prize.

The National Weather Service is forecasting temperatures to bottom out in the teens in north Alabama overnight. And the 20s will be felt all the way into south Alabama.

South Alabama has been under cold weather advisories for the past two nights and will have another one tonight, according to the weather service in Mobile.

The weather service in Birmingham has also added a cold weather advisory for many of its central Alabama counties tonight:

Cold weather advisories have replaced wind chill advisories, and the criteria varies from region to region.

Wind chills could be as low as 16 overnight in south Alabama.

Central Alabama wind chills could range between 10 and 15 degrees.

Here’s the forecast for low temperatures (air temperatures, not wind chills) tonight from the National Weather Service. North Alabama will be in the upper teens, central Alabama in the low 20s and south Alabama in the mid-20s:

It could end up being the coldest night of a very cold week. Low temperatures on Thursday night into Friday morning, when winter precipitation could be moving in, will be a bit “warmer.”

Here are the forecast lows for Thursday night into Friday morning. Lows will range from the upper 20s in north and north-central Alabama, the upper 20s to low 30s in central Alabama and the mid- to upper 30s in south Alabama, with some colder pockets in eastern Alabama:

Friday night into Saturday morning will again be very cold, but not as cold as tonight could be. Lows will be in the mid-20s in north Alabama, the upper 20s to low 30s in central Alabama, and the mid-30s in south Alabama:

Saturday night into Sunday morning will be in the running for one of the other coldest nights of the week. Temperatures could fall back into the teens in north Alabama, and 20s are expected for the rest of the state. Here are the forecast lows:

How long will this cold last? The National Weather Service’s forecasts go out only seven days, but the Climate Prediction Center has a probability temperature forecast for next week. It shows a high probability of below-average temperatures continuing through Jan. 17: