Setting the (temperature) record straight in the Northwest Territories

It was hot at the end of June throughout much of the Northwest Territories, but no all-time, territory-wide weather records were broken, at least not officially.

During that heatwave a temperature sensor at the Fort Smith airport recorded  39.9 C.

That June 30 temperature could have been a record for the N.W.T., but it's not been made official because it's based on data from the wrong temperature sensor.

The official hottest day registered in the Northwest Territories remains 39.5 C in Deline on Thursday, August 6, 2015. That Deline record broke the previous record of 39.4 C recorded in Fort Smith on July 18, 1941, something that has escaped notice on some fronts.

Whaddya mean 'wrong temperature sensor'?

Fort Smith has two weather stations. There's an Environment Canada climate station — built and maintained to exacting World Meteorological Organization standards — and a NAV Canada temperature sensor at the Fort Smith airport that isn't. 

The Environment Canada sensor generally provides official temperature records, but it was preoccupied on June 30.

Sara Hoffman, a meteorologist with Environment and Climate Change Canada in Edmonton, told CBC that it had gone into a routine diagnostic self-check late that afternoon. The good news is that the sensor works fine. The bad news is that it didn't record the temperature during the hottest part of the day.

"So ... at this time, we don't have an official value or daytime high for June 30, 2021," Hoffman said.

"What we can do is use the NAV Canada site as an estimate of the daytime high ... but that estimated value would not go into records or establish a record for the territory." 

The 39.9 C recorded at the Fort Smith airport is also the temperature reported in Environment Canada's historical weather data online, but with the caveat that it's based on incomplete data.

The Environment Canada climate station for Fort Smith did record 38.6 C on June 30, but that's not official either because of the self-diagnostic routine that turned the sensor off.

"Because the data is missing an hour, we unfortunately have to go through a process of quality control to see whether or not we can accept the data before it will make its way into our database," Hoffman said. 

Hotter day that doesn't count

Unofficially, it's been hotter in the territory — on July 20, 2002, a volunteer-run weather station at Rampart River recorded 40.6 C. This would have been the hottest day ever recorded in the N.W.T, but Environment Canada quality control experts had concerns.

"They were unable to unequivocally rule it [the recording] out, but they couldn't find data to corroborate it," Hoffman said. "We can't say that's an official record."

So officially, and for the record, the N.W.T. hot weather records are: Deline with 39.5 C on Aug. 6, 2015; Fort Smith with 39.4 C on July 18, 1941; and Fort Simpson, with 38.8 C on July 9, 2010.

But unofficially, temperatures hit 40.6 C at Rampart River in 2002, and on June 30 in Fort Smith it was 39.9 C.

So it was hot, what's the big deal?

Those high temperatures in Fort Smith were unusual for June.

The average temperature for June 30 is 23 C. That makes temperatures pushing 40 degrees on that day an anomaly. And it surpasses the previous high for the day by several degrees.

"The previous record for June 30 in Fort Smith was 31.7 C and that was set in 1955," Hoffman said.

The heatwave that hit the southern part of the territory was part of the widely reported heat dome now considered a one in 1,000-year event. Hoffman said scientific consensus blames human-caused climate change for the intensity of the heat.

"I can't think of a single other event where we've been able to say, 'The intensity of this event would not have been at this level had it not been for climate change,'" Hoffman said.