DENVER (CBS4) – The North American Monsoon is underway, and Colorado has been seeing increased moisture and afternoon storms as a result.

But the peak of the season is still at least a few weeks away, and some long-range forecasts say this year could be wetter-than-normal.


The word monsoon comes from the Arabic word “mausim” which means season.

Some people might be inclined to think that monsoon means heavy rain, because that is often what we see.

But the formal definition is simply a seasonal shift in the wind.

Because that wind shift often brings copious amounts of moisture into a normally dry or semi-dry region, we often associate a monsoon as being wet.


For Colorado, the monsoon wind shift means a flow from the south or southwest, which transports moisture into our state from the tropics, setting the stage for the daily cycle of afternoon showers and thunderstorms.

Severe weather is always a possibility when monsoon thunderstorms pop up, but the biggest threat, in addition to cloud-to-ground lightning, is for heavy rain.

That’s because the winds above Colorado that steer thunderstorms are light during the summer, so when a storm develops, it moves slow, increasing the chance for flash flooding.

Some of Colorado’s most deadly flash floods have happened during the last week of July, which is in the heart of monsoon season.


Colorado normally starts to feel the onset of the monsoon after the Fourth of July, but the activity really picks up between late July and the middle of August.

There is usually a pretty abrupt end around Labor Day as the days dry out and the seasons begin to change.

However, during a really active year, monsoon storms can last well into the month of September.

Most long-range forecast models point to much of Colorado having above normal precipitation this monsoon season. One reason is because of a developing El Niño.

While an El Niño is not currently happening, forecasters say there is a 70 percent chance that it will in the coming months.

During an El Niño year, the storm track typically shifts south, favoring more active weather across the central Rockies.


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