Dozens of people have died in Canada amid an unprecedented heatwave that has smashed temperature records.

Police in the Vancouver area have responded to more than 130 sudden deaths since Friday. Most were elderly or had underlying health conditions, with heat often a contributing factor.

Canada broke its temperature record for a third straight day on Tuesday – 49.6C (121.3F) in Lytton, British Columbia.

The US north-west has also seen record highs – and a number of fatalities.

Experts say climate change is expected to increase the frequency of extreme weather events, such as heatwaves. However, linking any single event to global warming is complicated.

The heat over western parts of Canada and the US has been caused by a dome of static high-pressure hot air stretching from California to the Arctic territories. Temperatures have been easing in coastal areas but there is little immediate respite for inland regions.

Before Sunday, temperatures in Canada had never passed 45C.

British Columbia Premier John Horgan said the hottest week the province had ever experienced had led to “disastrous consequences for families and for communities”.

The number of heat-related fatalities is likely to rise as some areas say they have responded to sudden death incidents but have yet to collate the numbers.

In Vancouver alone, heat is believed to have been a contributing factor in the unexpected deaths of 65 people since Friday.

“I’ve been a police officer for 15 years and I’ve never experienced the volume of sudden deaths that have come in in such a short period of time,” police sergeant Steve Addison said. Three or four a day is the normal number.

He said people were arriving at relatives’ homes and “finding them deceased”.

Dozens of officers have been redeployed in the city, while the increased volume of emergency calls has created a backlog and depleted police resources.

British Columbia Chief Coroner Lisa Lapointe said 100 more deaths than normal had been reported in the period from Friday to Monday.

The tiny village of Lytton, about 155 miles (250 km) east of Vancouver – and not much further south than London – has recorded all of Canada’s recent record highs.

Resident Meghan Fandrich said it had been “almost impossible” to go outside.

“It’s been intolerable,” she told the Globe & Mail newspaper. “We’re trying to stay indoors as much as possible. We’re used to the heat, and it’s a dry heat, but 30 [degrees] is a lot different from 47.”

Many homes in British Columbia do not have air conditioning as temperatures are usually far milder during the summer months. Temporary water fountains and cooling centres have been set up in the Vancouver area.

The country’s weather service, Environment Canada, has issued heat warnings for the provinces of British Columbia and Alberta, along with areas of Saskatchewan, the Northwest Territories and Manitoba.

In the US Pacific Northwest on Monday, temperatures hit 46.1C in Portland, Oregon, and 42.2C in Seattle, Washington, the highest levels since record-keeping began in the 1940s, the National Weather Service said.

At least a dozen deaths in Washington and Oregon are believed to be linked to the heatwave.

A doctor in a Seattle hospital told the Seattle Times the number of patients streaming in with heat stroke was comparable to the beginning of the Covid-19 pandemic.

Dr Jeremy Hess said some had kidney or heart problems, and one man had third-degree burns from walking on asphalt.

The heat has been intense enough to melt cables, shutting down the Portland Streetcar Service on Sunday.

An electrical utility in Spokane, Washington, has also introduced rolling blackouts to cope with huge power demand as residents run air conditioners.

Agricultural workers are often now being given the option to start at dawn and finish at noon. But labour contractors say that some stay regardless of the heat.

One worker was found dead in a field at the end of his shift at a farm in Oregon.

One Seattle resident told the AFP news agency that the city felt like a desert: “Normally… 60, 70 degrees [farenheit] is a great day – everybody is outside in shorts and T-shirts – but this is… ridiculous”.

Amazon allowed members of the public into areas of its Seattle headquarters as a cooling-off location on Monday, while people in Portland also flocked to cooling centres.

Lytton in British Columbia soared to 46.6C (116F) on Sunday, breaking an 84-year-old record, officials said.

A “heat dome” – static high pressure acting like a lid on a cooking pot – has set records in many other areas.

The US and Canada have both warned citizens of “dangerous” heat levels that could persist this week.

Experts say that climate change is expected to increase the frequency of extreme weather events, such as heatwaves. However, linking any single event to global warming is complicated.

BBC forecaster Nick Miller says that “heat dome” isn’t a strictly defined meteorological term but has become associated with describing large areas of high pressure, leading to clear skies and hot sunny days. The longer the high pressure pattern lasts, the longer the heatwave is and temperatures can build day by day.

This high pressure zone is huge, from California right up to Canada’s Arctic territories and stretching inland through Idaho.

Sales of air-conditioners and fans have surged, and cooling shelters have sprung up. Some bars and restaurants – and even a swimming pool – were deemed too hot to function.

Lytton, which is about 150 miles (250km) north-east of Vancouver, surged past the previous Canadian record.

That was set in two towns in Saskatchewan – Yellow Grass and Midale – back in July 1937 at a balmy 45C (113F).

Lytton was not alone. More than 40 other spots in British Columbia set new records.

Environment Canada senior climatologist David Phillips told CTV: “I like to break a record, but this is like shattering and pulverising them. It’s warmer in parts of western Canada than in Dubai.”

He said there was a chance of topping 47C somewhere, with Monday the likeliest day.

British Columbia’s power providers said there had been a surge in demand for electricity to keep air-conditioners running.

Environment Canada said Alberta, and parts of Saskatchewan, Yukon and the Northwest Territories, should also be on alert.

In its warning, it forecast a “prolonged, dangerous, and historic heatwave will persist through this week”, with temperatures 10C-15C above normal, at near 40C in many places.

The Pacific north-west has also been breaking records, particularly in parts of Washington and Oregon states.

The US National Weather Service called the heatwave conditions “historic” and said they would persist through the week, “with numerous daily, monthly and even all-time records likely to be set”.

Seattle and Portland, cities with famously rainy climates, both recorded their hottest temperatures ever on Sunday.

Portland shattered its prior record when temperatures reached 44C, according to the US National Weather Service. Seattle also passed a historic high as the mercury hit 40C.

Oregon eased Covid attendance restrictions to open up swimming pools and air-conditioned areas like shopping centres. But Seattle in Washington had to close one pool because of “unsafe, dangerous pool deck temperatures”.

Fruit growers have been rushing to pick crops, fearing the heat could shrivel cherries and other fruit. Pickers have been starting at dawn and stopping at lunchtime in the unbearable temperatures.

BJ Thurlby, president of the Northwest Cherry Growers, told the Seattle Times: “We are travelling in absolutely uncharted waters.”

The US track and field Olympic qualifying trials had to be halted in Eugene, Oregon, on Sunday, as the crowd was told to leave the stadium for safety reasons.

Some Covid vaccination centres also closed because of the heat.

Some areas along the coast could cool a little later in the week, but Boise, Idaho, could see a week of 40C+ temperatures. The National Weather Service said parts of the state could suffer “one of the most extreme and prolonged heatwaves in the recorded history of the Inland Northwest”.

The warnings for all were to stay hydrated, avoid strenuous activities, and check on vulnerable neighbours.