What type of clouds typically indicate the approach of a cold front?

The type of clouds that typically indicate the approach of a cold front are cumulus and cumulonimbus clouds.

Cumulus clouds are often seen in the early stages of cold front development; they form due to rising warm air ahead of the front. As the cold front moves in, it forces this warm air to rise, leading to the development of cumulonimbus clouds. These clouds are larger and more vertically developed, often associated with severe weather, including thunderstorms and heavy precipitation that can accompany cold fronts.

The presence of these clouds signals that a change in weather is imminent, due to the dynamic interaction between warm and cold air masses.