Brass Monkeys

5 December 2025

Today - some observations on the weather … and its effects on wildlife

This morning the temperature here in Montreal is -16C. There is little wind, but last night when there was was the “windchill” or the “Feels like” or whatever your local forecasting service calls it achieved -25C. The sky is a clear, pale blue. That photo above was taken yesterday afternoon and shows the St-Lawrence River ten minutes walk away from where I live - frozen across, as it will now stay for about three months. It’s cold. Not unbearably so, we have good coats and boots, but it should not be this cold quite so early in winter. We usually rely on December to let us acclimatize gradually - this has come as a shock.

What we are experiencing just now are January going into February temperatures, not the normal first week in December conditions! In Britain there is phrase that calls days like this Brass monkey weather, as in “it’s cold enough to freeze the balls off a brass monkey”. I don’t think I have ever heard it here in Canada, but it fits the bill.

Recently during our daily 7am garden bird counts we have had up to 15 or so species come to our feeders. This morning, barely seven and they came and hared back to shelter in brief blink of an eye and you’ll miss them dashes. The historical average for this date is somewhere between +1C and -5C and that is certainly what we have come to expect in the almost three decades we have lived here.

Why? What is happening? You can stay in the warm - I have done the research for you …

We have, I read, an early and exceptionally pronounced seasonal Arctic air mass intrusion when a strong high‑pressure ridge over central Canada funnels brutally cold air from north of us into our region. Hence the sub ‑20 °C air we are enjoying that is far colder than the maritime‑influenced air that usually moderates early‑December temperatures. Not only that. The polar jet stream has created a pronounced trough over eastern North America, which causes this influx of polar air. The Gulf‑Stream influence is limited and so the Atlantic’s usual moderating effect on eastern Canada is reduced.

Is climate change behind this? Yes - even though the overall long‑term trend is toward warmer winters. All that oil we are burning in our cars and so on is ultimately behind the effect on the brass monkey’s nether regions. At this point I turned to my friends at the Proton AI website to try to winkle out more detail … I think I understand. Quote:

Why an Arctic‑driven cold snap can happen in a warming world

Arctic amplification – The Arctic is warming roughly twice as fast as the global average. Thinner sea‑ice and reduced snow cover change the temperature gradient between the pole and mid‑latitudes. This weakens the polar vortex and makes it wavier, allowing pockets of frigid Arctic air to spill southward. When the vortex becomes distorted, a jet‑stream trough can dip far enough to push Arctic air masses into eastern Canada. Researchers have linked an increase in such troughs to the loss of Arctic sea‑ice and to changes in the stratospheric wind patterns (the quasi‑biennial oscillation). While average winter temperatures rise with climate change, the variance of temperature also grows. That means the tails of the distribution—both very warm and very cold events—become fatter. In practice, this translates into occasional, sometimes severe, cold spells occurring more frequently than they did a few decades ago. Lastly, Montreal sits in the St. Lawrence River valley, a natural conduit for north‑south airflow. When a strong Arctic trough aligns with the valley, cold air can pool quickly, amplifying the temperature drop.

Now you know.