The weatherman is calling for thunderstorms tonight, as “monsoon moisture returns to the state.”
I always feel weather forecasters are a little presumptuous calling summer moisture in Colorado monsoons.  I mean, although we can have the occasional gully-washer, our piddly precip is nothing compared with the six months of torrential rain that most people normally think of when they hear the word monsoon.
But according to weather people, “a monsoon is a wind that changes direction with the seasons”. By that definition, the Southwest, with Colorado on it’s northern edge, has a monsoon.  Summer heat on the desert of Southwest Arizona, California, old and New Mexico warms the air there, causing it to rise.  This creates a vacuum, called a low pressure cell.  The low pressure sucks moist air from the Pacific and Gulfs of California and Mexico, bringing storms to the west and southwest part of the state and

occasionally onto the plains. In winter, the Southwest deserts cool, and create a high pressure cell that can keep moisture out.
These summer storms don’t compare to the classic monsoons of Asia and east Africa, but Coloradoans are usually glad to get moisture in any form.