As 2016 draws to a close, so does this brief period of rather pleasant winter temperatures in Whitehorse.

The mercury is expected to drop below -20 C over the weekend.

It will likely hover around there for the first week of January, at least, said Ross Macdonald, a meteorologist with Environment Canada Weather.

Last year’s El Niño brought warmer than average winter temperatures to the Yukon, but now La Niña has arrived – and with it, chillier weather.

El Niño and La Niña refer to ocean-atmospheric interactions that give rise to respectively warmer or cooler weather conditions around the world.

The phenomena are determined by sea surface temperatures in the equatorial Pacific Ocean.

Sea surface temperatures that are higher than normal produce El Niño, and lower than normal temperatures create La Niña.

Last year, there was a significant El Niño, said Macdonald, with sea surface temperatures reaching two degrees higher than normal.

This year’s La Niña is rather weak by comparison, with temperatures just 0.7 degrees below normal.

“We’re kind of riding that line, that threshold, where we do define a La Niña. It’s particularly weak but it is still defined as La Niña at this time,” he said.

El Niños and La Niñas are regular climatic phenomena. A milder La Niña is not necessarily linked to climate change, said Macdonald.

What this minor La Niña means for the territory this year is something closer to an average Yukon winter.

This December, however, was decidedly colder than usual, said Macdonald.

The average temperature in Whitehorse in December is -12.5 C.

This year, it was -16 C.

The coldest day this month was Dec. 15, when temperatures sank to -35.6 C. The warmest day was Dec. 19, when the mercury inched above zero, hitting 0.6 C.

Whitehorse temperatures are measured at the Erik Nielsen Whitehorse International Airport.

The two-week cold snap earlier this month, which saw the mercury dip well below -30 in Whitehorse and colder elsewhere, drove the average temperature down, said Macdonald, but it didn’t break any records.

“In terms of how that ranks overall, with historical context, it’s certainly colder than normal, but it hasn’t been dramatically colder than normal,” he said.

Whitehorse was graced with relatively mild winter weather around Christmas, but temperatures are set to tumble back down starting Saturday.

“It will be the beginning of a new cold snap,” said Macdonald.

“Not perhaps as harsh as the first one, at least at this initial stage, but it will be sunny and cold for New Year’s Eve and New Year’s Day.”

The first week of 2017 will see below-seasonal temperatures with daytime highs around -18 C and overnight lows in the mid-minus 20s.

But at least it will be sunny – for the first half of the week, anyway.

December was also drier than normal, said Macdonald.

“Not dramatically so, but certainly it is on the dry side.”

There are 19 cm of snow on the ground at the airport, with 9 cm of that having fallen this month.

Usually about 23 cm of snow have fallen by this time of year, said Macdonald.

The snowiest day this month was Dec. 2, when six cm fell.

“We are sitting at this month being a drier than normal month, again, not dramatically so, but certainly it is on the dry side,” said Macdonald.

It’s too hard to say at this point if chilly winter temperatures will persist through March, said Macdonald.

Alaska preparing for heavy snow.