A monsoon storm roared in unexpectedly Sunday evening capping off a month of triple-digit temperatures.

At least three lightning-related fires, including one in the Catalinas, were reported in and around the city.

Tucsonans baked in triple-digit heat for 30 days straight throughout the entire month of June. It's the first 30-day month to reach 100 degrees or higher every day, according to the National Weather Service.

Thunderstorms moving south from Clifton picked up speed and dust as they crossed through Cochise County and into Benson at the same time a storm was developing over the Rincon Mountains and into Vail. The combination of outflows from both storms kicked up dust, causing the weather service to issue a dust storm warning in Pima County, said Chris Rasmussen, a meteorologist with the weather service.

Some people reported zero visibility near Davis-Monthan Air Force Base, Rasmussen said.

The wind continued to accelerate as the storm headed west, Rasmussen said.

Gusts as high as 68 mph were reported at Tucson International Airport shortly before 7 p.m.

A 40-acre fire broke out Sunday evening in the Santa Catalina Mountains, just west of milepost 8 on Catalina Highway in an area known as Prison Camp, said Heidi Schewel, a spokeswoman for the U.S. Forest Service.

The fire was possibly caused by a lightning strike, Schewel said.

Tucson fire crews also were called to two lightning-related house fires.

The first was in the 9100 block of East Elderberry Street near East Valencia Road and East Old Vail Road just after 6:30 p.m.

A 911 caller reported seeing the house struck by lightning and sparks coming from the roof, said Capt. Barrett Baker, a Tucson Fire Department spokesman.

Nobody was home at the time, and crews extinguished the fire from the exterior.

The second fire broke out just before 7 p.m. in the 2100 block of South Farwell Avenue, near South Rosemont Avenue and East 29th Street.

Callers reported smelling smoke, and crews found a fire in the attic space of the house.

The residents were safely evacuated, Baker said.

Areas in Tucson received between a tenth of an inch and more than a third of an inch of rain.

The storm caused temperatures to drop by more than 25 degrees within an hour.

The temperature at 6:30 p.m. was 107 degrees and by 7:28 p.m. it had dropped to 81 degrees, Rasmussen said.

Monsoon activity typically picks up around the Fourth of July, Rasmussen said.

"This is just on track. We're just starting off the season," he said.

The heat wave is expected to continue into July. Today there is a 30 percent chance of rain as well as on Tuesday, and a 40 percent chance on Wednesday. But temperatures highs are still expected to top 100-degree mark.

Highs between 101 and 105 degrees are expected through the weekend.

On StarNet: View current conditions and get the 10-day forecast at azstarnet.com/weather

Contact reporter Veronica Cruz at vcruz@azstarnet.com or at 573-4224.