California wildfires have burned five times the average area this year, officials say

California’s wildfire season is off to a ferocious start, with the state’s top wildfire official saying that fires have already burned through five times the average amount of land for this time of year.

Speaking at a news conference on Wednesday, Joe Tyler, the director of the California department of forestry and fire protection (Cal Fire), said the state has responded to more than 3,500 wildfires so far this year. Together, those fires have scorched nearly 220,000 acres – more than five times above what is typical for mid-July, which is considered fairly early in the state’s wildfire season.

Related: Las Vegas sets record for number of days over 115F amid its ‘most extreme heatwave in history’

“We are not just in a fire season, we are in a fire year,” Tyler said at the news conference. “Our winds and the recent heatwave have exacerbated the issue, consuming thousands of acres. So we need to be extra cautious.”

Authorities across the US west have warned of the rising risk of wildfires amid a protracted heatwave that has dried out the landscape and smashed temperatures records from California to Oregon to Nevada.

“Climate change is real,” said California’s governor, Gavin Newsom, on Wednesday. “Those extremes are here present every day in the great state of California.”

An abundantly wet winter has left landscapes across California coated in grasses that quickly dried as the weather warmed, creating abundant fuel for fast-burning brush fires.

California crews were working in scorching temperatures to battle numerous wildfires on Thursday, including a stubborn 34,000-acre blaze known as the Lake fire , which prompted evacuation orders for about 200 homes in the mountains of Santa Barbara county, north-west of Los Angeles.

In Oregon on Thursday, crews were battling the Larch Creek fire , which has grown to more than 11,000 acres since Tuesday. Lower temperatures and calming winds were helping the crews’ efforts, but the local fire danger level remained extreme. One firefighter was treated for heat-related injuries.

In Hawaii, Haleakala national park on Maui was closed as firefighters battled a blaze on the slopes of a mountain. Visitors in more than 150 vehicles that had gone up on Wednesday for the famous sunset views were not able to descend until about 4am on Thursday because the narrow roads were blocked by fire crews.

More than 63 million people in the US remained under heat alerts on Thursday, as forecasters predicted some relief from the heat was due by the weekend.

Las Vegas set a new record on Wednesday when it saw its record fifth consecutive day of temperatures sizzling at 115F (46.1C) or greater. Already, Nevada’s largest city has broken 16 heat records since 1 June “and we’re not even halfway through July yet”, a National Weather Service meteorologist, Morgan Stessman, said on Wednesday.

That includes an all-time high of 120F set on Sunday, which beat the previous 117F record.

Related: ‘Like an oven’: death at US women’s prison amid heatwave sparks cries for help

The heat has been suspected in deaths across multiple states. In California, officials in the Silicon Valley county of Santa Clara are investigating 19 potential heat-related deaths, including three homeless individuals, the county’s medical examiner-coroner’s office said in a statement on Thursday. And in Oregon, the number of potentially heat-related deaths has risen to 10, according to the state medical examiner’s office.

Heat was blamed for a motorcyclist’s death last weekend in Death Valley national park and the National Park Service is investigating the third death of a Grand Canyon hiker in recent weeks. Arizona authorities are investigating deaths of a two-year-old and a baby in separate incidents, and in Nebraska, Omaha police say a boy died after being left in an SUV.

Read more on wildfires and heat in the US

• Las Vegas sets record for number of days over 115F amid its ‘most extreme heatwave in history’
  ‘Like an oven’: death at US women’s prison amid heatwave sparks cries for help

• US wildfire season has arrived. Here’s why it could be an explosive summer