The Northwest Territories broke a symbolic temperature barrier as a heatwave continued on Tuesday, reaching 20C in March for the first time since records began.

Yohin Lake, near Nahanni Butte, posted a Tuesday high of 21.6C. The NWT’s previous March record was held by nearby Fort Liard, which reached 19.9C on March 29, 2016.

Most of the territory sweltered in record or near-record temperatures, triggering concern over rapidly disintegrating ice roads, a call in some quarters for government action on climate change, and even a warning about rotting meat.

The Mackenzie Valley winter road was formally closed by the NWT government early on Wednesday.

The territory’s Department of Infrastructure said stranded Sahtu residents would be given help to get home with the road now shut.

“A plan is being developed,” the department said on Twitter.

The week’s weather was exceptional on a century-long scale.

“The dataset at Yohin Lake goes all the way back to 1959. Other datasets go back to the early 1900s and nothing in the data is above 20C in March. This hasn’t happened for at least a good 100 years, so it’s pretty rare,” said Patrick Duplessis, an atmospheric scientist at Dalhousie University, who closely follows northern weather records.

“This is historic,” said Rob Paola, a former severe weather meteorologist with Environment Canada who recently retired after more than 30 years of forecasting.

“Incredibly, it’s occurring on March 19 – not the end of the month when it’s climatologically warmer.

“Daytime temperatures are running some 20-25C above normal, which is extraordinary.”

Paola said the warm weather is being caused by “a massive upper ridge” over British Columbia and the Yukon, bringing unseasonably warm air to northwest Canada.

“The stronger March sunshine and downslope winds off the Mackenzie mountains have allowed temperatures to rise to record levels, especially just east of the mountain range – kind-of like a chinook effect,” said Paola.

From Ulukhaktok to the Nahanni’s Rabbitkettle Lake, well over a dozen NWT weather stations set record mid-March highs on Tuesday – most of them by a significant distance.

Temperatures are forecast to cool somewhat, but remain well above freezing, across much of the territory on Wednesday and Thursday.

‘Check your freezer’

The extraordinary heat made some of the NWT’s winter road system all but impassable on Tuesday, as territorial authorities restricted travel on many roads to night-time only, while warning the roads could close for the season at any moment.

Gordon and Freda Taneton, from Délı̨nę, shared photos on Facebook of a treacherous journey along the Mackenzie Valley winter road in which their truck, facing hopelessly muddy conditions, required the assistance of heavy equipment on caterpillar tracks to make it through.

As of Wednesday, only the Mackenzie Valley winter road had officially closed for the season, but daytime travel and weight restrictions existed on a range of roads. Check the NWT government’s highway conditions page before you set out.

The Snowcastle at Snowking’s Winter Festival in Yellowknife will remain closed from 12-5pm on Wednesday to protect the rapidly softening snow.

Seizing on that development – and festival organizers’ decision to link the closure to climate change – Ecology North, the Yellowknife-based environmental non-profit, issued a news release on Tuesday urging the territorial government to better combat climate change’s causes and effects.

Calling on the territory to “unleash innovation,” Ecology North suggested more local food production alongside improvements to renewable energy production and distribution.

“There are so many solutions out there. We just need the leadership to put them in place,” said Craig Scott, Ecology North’s executive director.

Coincidentally, the NWT’s hottest March day on record happened also to be federal budget day – in which finance minister Bill Morneau promised $18 million over three years to help the NWT begin its Taltson expansion project, which is designed to hit some of the targets Ecology North mentioned.

The NWT envisages Taltson’s expansion leading to cheaper, greener power across the North Slave and beyond. However, the eventual price tag for the full project is expected to exceed $1 billion – far beyond the $20 million or so, in total, committed by the federal and territorial governments to date.

Recently, some federal money has been made available specifically to help the NWT prepare for climate change.

Around $200,000 will pay for a project estimating the cost of climate change’s impact on the NWT over the next two decades, and the costs and benefits of mitigating actions the territory could take.

Meanwhile, out on the land, environment officers issued a warning after coming across discarded meat near Marian Lake in the North Slave.

Two shoulders, neck bones, and an old turkey were found on a portage in the area on Sunday. Images of the find were shared by the territorial government on Tuesday.

“Wild meat that is spoiled or freezer burnt should not be discarded on the land, especially near communities, as it can attract other animals such as bears or wolves,” read a message from the Department of Environment and Natural Resources.

“As the weather is warming, please check your freezer to make sure it is plugged in and in working order. Allowing edible wild meat to spoil is an offence under the Wildlife Act.”

‘Definitely worrying’

Asked if Ecology North and Snowking’s Winter Festival organizers were right to link this week’s unprecedented temperatures to climate change, Dalhousie’s Duplessis and retired meteorologist Paola were hesitant to unconditionally concur – but did see the heat as part of a broader, indicative pattern.

“I don’t want to say this is caused by climate change, as the NWT has experienced warm weather in March in the past – although not to this extent,” said Paola.

“However, a warmer climate does make these unseasonably warm episodes more likely in the future.

“Note that the previous warmest March temperature in the NWT was 19.9C, set just three years ago, in 2016.”

“It does look like there are more and more ups and downs,” agreed Duplessis.

“I wouldn’t say this one event is necessarily fully associated with climate change, but these extreme highs – or extreme lows, sometimes – do seem to be happening more and more.

“It’s definitely worrying to see 20C at this time of year, when there is still snow on the ground.”