There's a heatwave coming to the Mother Lode with daytime highs approaching or exceeding triple digits by this weekend.

In Sonora, the daytime high Monday peaked around 80 and it could be as much as 20 degrees hotter by Saturday and Sunday. Tuesday is supposed to get up around 90 in Sonora.

Places like San Andreas, Angels Camp, Chinese Camp and Moccasin could see highs in the upper 90s to the low 100s from Wednesday to Sunday.

Forecasters with the National Weather Service in Sacramento say the heat is due to high pressure building across northern California.

People who are especially sensitive to summertime heat and heat-related illnesses, including toddlers, small children and the elderly, should avoid prolonged exposure to direct sun when temperatures climb into the upper 90s later this week in Calaveras and Tuolumne counties.

The hottest day of the heat wave could be Saturday. Forecasters say north winds in some areas Saturday could increase the potential for fire starts and the spread of fires.

Personnel with the Cal Fire Tuolumne-Calaveras Unit responded to at least three fires Monday and Sunday.

The most recent was reported just after 10:30 a.m. Monday in the 17000 block of Harvard Mine Road at Highway 108 southwest of Jamestown, Lindy Shoff with Cal Fire in San Andreas said. The fire burned a spot of vegetation, one engine crew responded, and they declared it contained at 10:44 a.m. No injuries were reported. The cause of the fire was being investigated.

At 4 p.m. Sunday in Linden, a fire was reported in the 12000 block of Wimer Road near Highway 26, about 5 miles west of Jenny Lind in Calaveras County, Shoff said. The fire burned 3.75 acres of vegetation and four engine crews, one bulldozer and two water tank trucks responded. The fire was declared contained at 4:29 p.m. No injuries were reported and the cause of the fire was being investigated.

About an hour earlier at 3:05 p.m. Sunday, a fire was reported at the Camanche Marina South Shore at Camanche Reservoir on the Mokelumne River. The fire burned a spot of grass and one engine crew responded. They declared the fire contained at 3:11 p.m. A vehicle was damaged by the fire. No injuries were reported. The cause of the fire was being investigated.

Changing weather sometimes prompts extra movement among deer and other mammals in the Stanislaus National Forest. About 7 p.m. Sunday a vehicle struck a bear on Highway 108 west of Pinecrest. The bear appeared to be a brown juvenile or adult bear.

The California Highway Patrol reported the incident about 7:30 p.m. Faustino Pulido with CHP Sonora said a blue Subaru Baja struck a bear on Highway 108 west of Old Strawberry Road, near Mia’s. A caller said the bear was injured in the road. A CHP officer responded and found the bear dead on the right shoulder. Whoever struck the bear was gone.

“California Department of Fish and Wildlife were notified and the bear was dragged out of sight from the passing motorists to be later picked up,” Pulido said.

Staff with the Stanislaus National Forest did not respond to requests for information about the bear incident.

Over in Mariposa County on Monday, a wildfire southwest of Coulterville prompted mandatory evacuations and an evacuation advisory for the town of Coulterville. The fire was reported about 12:30 p.m. Monday at Wheeler Gulch Road and Highway 49.

As of 3 p.m. the Wheeler Fire had burned 90 acres and no part of it was contained, Jaime Williams with Cal Fire Madera-Mariposa-Merced Unit said in phone interviews.

There were m andatory evacuations for Mary Harrison Mine Road, Old Highway 49 Road, Crown Lead Road, and Highway 49 between Crown Lead Road and Highway 132. The evacuation advisory for the town area of Coulterville was not mandatory.

An American Red Cross shelter was set up at Lake Don Pedro Elementary, 2411 Hidalgo Street, in La Grange, Williams said.

There were no estimates on the numbers of aircraft and engine crews assigned to the fire, or if there were any structures damaged or destroyed. No injuries had been reported as of 3 p.m. The cause of the fire was being investigated.

Also in Mariposa County, a fire that broke out Friday outside Bootjack east of Mariposa and prompted evacuations and destroyed one structure was said to be 85 percent contained as of 10 a.m. Monday.

The fire burned next to a tree mortality area near the community of Lushmeadows, staff with the Madera-Mariposa-Merced Unit said in an update. Lushmeadows is about 65 miles southeast of Sonora.

Staff with the Madera-Mariposa-Merced Unit announced Monday afternoon all burn permits for outdoor residential burning of landscape debris such as branches and leaves are now suspended. They said it’s because in the wake of a relatively wet winter, warming temperatures and dry winds are now quickly drying out abundant annual grasses. There’s increased fire danger posed by high volumes of dead grass and hotter, drier conditions in the Madera-Mariposa-Merced Unit area.

Forecasters on Monday said the approaching heat wave will include a period of excessive heat Friday, Saturday and Sunday. The heat could affect people and animals.

Long outdoor exposures will increase chances for heat related illness, especially for sensitive groups, National Weather Service staff in Sacramento said. In addition, livestock could suffer heat stress with limited cool temperature recovery and relief from heat overnight.

Contact Guy McCarthy at or 588-4585. Follow him on Twitter at @GuyMcCarthy.