Here's why:

* Warm fronts bring warm, moist air that gradually rises over the cooler, denser air ahead of the front.

* This slow, gentle lifting creates a widespread, stable layer of air, perfect for the formation of stratus clouds.

* The clouds are typically low-lying, gray, and produce light drizzle or mist.

While stratus clouds can sometimes occur in other situations, such as under stable conditions with light winds, their association with warm fronts is particularly strong.