Another wet monsoon season may be coming to the Valley, according to weather experts.

During a briefing on Thursday sponsored by the University of Arizona, climatologists said there are indications of an early onset and high intensity to the summer's thunderstorms, at least early on.

"We think (the monsoon) will start strong and be strong into July," said Erik Pytlak, a meteorologist with the National Weather Service in Tucson.

Last year, these experts accurately predicted the coming monsoon would pack stronger, more frequent thunderstorms in the state.

Phoenix's official rainfall total for the 2008 monsoon season was 5.7 inches - more than double the average amount of 2.77 inches. And Mexico had its wettest June-through-September stretch since at least 1941.

A decade has passed since the Valley had consecutive summers with above-average rainfall.

The monsoon is the summer phenomenon of humid air flowing northward into the Southwest. When the monsoon is in full force, muggy days can lead to stormy afternoons.

These summer thunderstorms are responsible for about one-third of the Valley's annual precipitation.

Monsoon season begins June 15 and lasts through September.

The climatologists said they look for clues, to divine the monsoon's arrival and strength, in such wide-ranging areas as drought conditions in Texas and thunderstorms in Southeast Asia.

Christopher L. Castro, an assistant professor in the University of Arizona's Department of Atmospheric Sciences, said there are "large-scale signals" of the monsoon arriving sooner than later and bringing rain almost immediately.

However, the experts said forecasts were difficult to make for the monsoon's later half.

To blame was the growing warmth of tropical Pacific Ocean waters. This weather pattern, known as an El Nino, can snuff out the monsoon - but it can also lead to wet autumns in the Southwest.