Clear skies, calm winds and longer autumn nights combine to form dense fog and frost — know what to inspect on your car before that first chilly commute.

A frontal boundary is stalled out across the Midwest and Central Plains, leading to a multi-day flood threat. Cities like Chicago need to be prepared.

We have the maps you need to monitor the tropics, including tracks, current weather and other areas to watch.

A coastally trapped wave of warm water is creeping toward California, pushing sea levels higher. The real danger comes when winter storms arrive.

Lightning heats air to 30,000 degrees Kelvin, hot enough to crack nitrogen apart and send it down in the rain as natural fertilizer. Here's the chemistry.