North American Monsoon Arrives, Season Runs June 15-September 30

By Chris Spears

DENVER (CBS4) - When you hear monsoon you probably think about heavy rain and thunderstorms, or maybe flash flooding.

But the term actually has more to do with wind.

A monsoon is a seasonal shift in the wind pattern that transports moisture into an area which helps to produce afternoon showers and storms.

In North America that moisture comes from both the Gulf of Mexico and the central Pacific Ocean.

The monsoon starts showing up in mid-June for places like Arizona and it can last through September.

In Colorado we normally start to see the monsoon's influence during July and August with it ending around Labor Day.

Moisture moving in from the south this weekend looks like monsoonal moisture on a map but it's really related to what was once Hurricane Bob and a low pressure sitting in the Pacific Northwest.

Meteorologist Chris Spears travels weekly in the CBS4 Mobile Weather Lab reporting about Colorado's weather and climate. Check out his bio, connect with him on Facebook or follow him on Twitter @ChrisCBS4.