Monsoon storms move across Arizona, bringing tornado warning

Metro Phoenix could see some rain and blowing dust on Wednesday evening as a storm system pushes north from southern Arizona, officials said.

The National Weather Service in Phoenix said showers and storms were expected to begin in southern Arizona on Wednesday afternoon, pushing north toward metro Phoenix in the evening.

Austin Jamison, a meteorologist with the National Weather Service in Phoenix, said that the highest chance of storms was later Wednesday afternoon when storm chances would increase from 10-20% of rain to 30-40%.

The storms could bring gusty winds and blowing dust was also possible, the weather service warned.

No measurable rain had fallen in metro Phoenix as of 5 p.m. Wednesday, according to the Maricopa County Flood Control District's rainfall map .

While the rain wasn't expected to set in until the afternoon, the preceding cloud cover helped drop temperatures from the high of 105 degrees at about noon to the mid-90s by 2 p.m.

Jamison said storms could also be possible on Thursday afternoon when chances of rain reach 30-40% before falling overnight.

Elsewhere in the state, the National Weather Service issued warnings on tornadoes, flash floods and thunderstorms.

Tornado warning issued for Cochise, Graham counties

The National Weather Service briefly issued a tornado warning for Cochise County and Graham County. It started at 3:47 p.m. Aug. 21 and ended roughly a half hour later, at 4:15 p.m.

Flash flood warning issued for Coconino County

The National Weather Service has issued a flash flood warning for Coconino County starting at 3:36 p.m. Aug. 21. The warning expires at 9:45 p.m. Aug. 21.

Thunderstorm warning issued for Pima County

The National Weather Service has issued a flash flood warning for Coconino County starting at 3:36 p.m. Aug. 21. The warning expires at 9:45 p.m. Aug. 21.

For the latest watches and warnings, see our weather alert page .

What happens during a monsoon?

This desert weather phenomenon can look very different in an urban environment such as Phoenix, compared with the saguaro-dense hills of the Sonoran Desert.

According to the weather service in Phoenix, high pressure in the atmosphere over northern Mexico strengthens and drifts northward during the summer months, which causes a reversal in the weather pattern across the Southwest.

While storms typically move from west to east in the spring, storms will move from east to west in the summer.

This flow then causes high levels of moisture to gather in the atmosphere across the desert landscape as tropical air moves north, according to the weather service.

With the combination of summer heat and moisture, conditions are more likely to become more favorable for periodic rain showers and thunderstorms.

Typically, the month of July is the rainiest of the year in Phoenix. About 1 to 1.05 inches of rain is expected. That's preceded by the driest month of the monsoon, June, which has an average rainfall of 0.02 inches.

Arizona Republic reporter Raphael Romero Ruiz contributed to this article.

This article originally appeared on Arizona Republic: Monsoon storms move across Arizona, bringing tornado warning