Ashcroft made it into the record books on Wednesday, Sept. 3, when it recorded an official temperature of 40.8 C (105.4 F).
It wasn’t just the hottest spot in the country on that date: the temperature of 40.8 C was the hottest temperature ever recorded anywhere in Canada in the month of September. The previous hottest September temperature ever recorded in the country was 40 C, a three-way tie between Morden, Manitoba in 1906, Lost River, Saskatchewan in 1940, and Lytton, which hit 40 C on Tuesday, Sept. 2, 2025.
Lytton was still hot on Sept. 3, reaching 39.8 C. It was one of 16 B.C. communities that set new temperature records on that date, including Clinton (34.3 C), Kamloops (36.9 C), and Lillooet and Merritt (both 38.7 C). The previous record highs for that date took place in the last 40 years apart from Clearwater, which broke a record that had stood since 1950, and Lillooet, breaking a record that had stood since 1934.
“We had a big high pressure system blocking out to sea low pressure systems, which were trapped and unable to come ashore,” says Joey Onley. Based in Wells, he has been studying weather and climate for four decades and specializes in the weather of the B.C. Interior. “They rotate counter-clockwise, pulling warmth up from the south.”
He adds that such high temperatures so late in the summer are unusual.
“As we come into the later part of the year the angle of the sun is lower, so there are fewer hours of daylight. Also, the position of the sun isn’t directly overhead, so some energy of the sun is deflecting off the planet. In summer it’s pounding straight down, but in winter the sun is so low there’s barely any heating power getting in.”
Putting the unseasonably high early-September temperatures in B.C. in perspective, Onley says you only have to look at where else in the world was recording those sorts of temperatures at the same time.
“Where else is 40 C happening? Iraq and Saudi Arabia, which are way south. People are trying to convince me this is normal, that this is summer. No, it’s not. People say this is typical, but it’s not. We used to have entire summers in Wells where it never got above 30 C, but for years now it’s been getting higher than that consistently.”
Onley gets frustrated when he hears people claim that a modern spell of unusually hot weather is “the way it used to be,” or that they remember other times when it was this hot at this time of year.
“Every time we hit this new level of bizarre they will tell you they remember when it was this hot back in the 1980s. A town like Penticton never hit 40 C in the entire 1980s, but people there will tell you ‘I remember back in the 1980s when it was like this.’ Or they’ll remember an instance from when they were a kid when it happened at the beginning of July and ascribe that to this time of year.
“Memories are faulty. The human mind is a bad collector of knowledge, and it’s not that reliable. People move the goalposts, or remember things the way they want to remember them. Human experience is anecdotal, which is why in the realm of the courts it’s not good evidence.”
He also has a few words for people who post pictures of their backyard thermometers, which often show temperatures that are quite different to the official ones from Environment Canada. These are collected at weather stations, and Onley notes that that these are constructed and placed to ensure that nothing can influence the data that isn’t the data itself.
“It can’t be near buildings, or pavement that can radiate heat out. It has to be two metres off the ground, so it doesn’t get radiant heat. It needs to be in a place that’s representative of the region, but can’t be influenced by anything around it.
“I frequently have people posting pictures on Weathers Watchers [Interior Weather & Wilderness Watchers, Onley’s Facebook page] showing a mercury thermometer in direct sunlight. Weather station thermometers are only reading the air temperature, and a direct sunlight temperature will be different to air temperature. So people say ‘It was 45 C in 1983,’ but the data says it was 38 C.
“You need data that’s pure and true, and only verifiable weather stations can provide that. In science, experiments need to be free from bias and influencing factors. People’s personal stations can be helpful to give a picture of what’s going on, but we can’t verify that your weather station was working 100 per cent, so it’s no more than a circumstantial picture.”
Onley adds that 40 C temperatures in B.C. are not normal.
“Between Aug. 15 and Aug. 30 there are only three time periods where B.C. hit 40 C for four days in a row, so it’s anomalous. August is not a month where it hits 40 C a lot. Don’t start thinking of 40 C as a normal value. It’s not. People confuse ‘it happens’ with ‘it’s normal.’ Yes, 40 C happened, but it’s always an extreme temperature.”
Despite summer 2025 feeling like a “down” year in B.C., Onley says that temperatures around the province have still been above the historical average.
“Maybe not greatly, and we had some down periods, but we also had some extremely hot periods to counteract that. We have these short-term memories where people are becoming so used to B.C. being so extremely hot that a year like this feels like a down year when actually it’s slightly above average.”
As for Ashcroft’s record-setting Sept. 3?
“Ashcroft hitting 40.8 C is great for Ashcroft,” says Onley. “Ashcroft is a desert climate, and it deserves an all-time record.”
For more information about B.C. Interior weather, check out the Interior Weather & Wilderness Facebook page, as well as Onley's YouTube channel, Joey Only - Cariboo Weather Dude.
