A rash of vehicle wrecks Monday on drizzle-dampened roads throughout the region left several people injured and blocked some busy routes, according to the CHP.

“Officers have been responding to back-to-back calls all morning,” said CHP Officer Jon Sloat, who tallied 20 crashes in Sonoma County between 6 a.m. and 3 p.m. “Most (officers) attributed them to unsafe speed for the wet roadway conditions.”

The first day of June in Santa Rosa is typically sunny with a high of 78 degrees, but Monday dawned dark gray with heavy, dripping fog.

Umbrellas, hooded jackets and windshield wipers were required for many on the first day of a month that sees the end of school and the start of summer.

“It’s been awhile since we’ve seen this much water on the road,” said Steve Anderson, meteorologist with the National Weather Service in Monterey.

Anderson said a small front moving through the area wrung whatever moisture it could find out of the atmosphere. The North Bay’s weather should improve incrementally each day this week, he said, with diminishing fog and afternoon temperatures in the upper 70s.

That bodes well for many of Sonoma County’s high schools, which will hold graduation ceremonies later this week.

“It’s transitioning to summer,” Anderson said. “Good graduation weather.”

But early Monday, with the roadways as wet as they’ve been in some time, crash reports were cropping up at a steady rate on the CHP’s North Bay traffic website.

Crash locations included Calistoga Road at Porter Creek Road, Highway 12 west of Sebastopol, Highway 101 at Highway 12 in Santa Rosa, Stony Point at Roblar roads and, in Napa County, Butts Canyon Road and Tubbs Lane.

Sloat said the most serious crash in Sonoma County occurred at 10:15 a.m. on Calistoga Road near Porter Creek Road when motorcyclist Stephen O’Brien, 48, of Calistoga crashed on the wet roadway and fractured a leg. He was taken to Santa Rosa Memorial Hospital. The collision also temporarily blocked the southbound lane of the busy route between Calistoga and east Santa Rosa.

At 8:50 a.m. a three-vehicle crash on Highway 12 west of Sebastopol blocked that route for more than an hour. The crash, near Furlong Road, sent two people to Santa Rosa Memorial Hospital with moderate injuries.

The crash also caused an oil spill, requiring a response from a county roads crew.

One of the early morning crashes involved a man suspected of drunken driving with two prior DUI convictions and five license suspensions, Sloat said.

The 8:15 a.m. crash on Sebastopol Road at West Avenue involved driver Pablo Vazquez-Sanchez, 26, of Santa Rosa, who hit the back of a vehicle stopped at a red light. Vazquez-Sanchez appeared to be intoxicated, failed sobriety tests and was arrested.

Underneath his car, officers found two beer cans they believe he stashed there. One of the cans was open, Sloat said.

He was booked into Sonoma County Jail.

You can reach Staff Writer Randi Rossmann at 521-5412 or randi.rossmann@press democrat.com or Twitter @rossmannreport.