La Niña is a cyclical weather event caused by lower-than-average sea temperatures in the eastern Pacific, which can trigger extreme weather events, particularly in Asia, the Americas, and Australia.

BMO said latest forecasts suggest a 90% chance of La Niña conditions lasting through the North Hemisphere's winter, and a 50% chance of their persisting into spring of 2022.

"Just as with previous La Niña events, we foresee some potential supply-side disruption to metals and bulk commodities over the coming months, which in certain cases could yield potential price gains," BMO said.

BMO noted that all recent La Niña periods have been bullish for commodity prices. It also noted that that markets could be particularly vulnerable given the shortage of inventory to buffer supply disruption, with copper exchange stocks at the LME recently hitting their lowest levels in nearly 50 years, and lead and tin stocks also depleted.

"Supply disruption would likely put further strain on supply chains, potentially stoking inflation," BMO said.

In particular, BMO pointed to a harsh winter in China, which could exacerbate existing power shortages there.

"China's power situation remains precariously balanced," BMO said. "With blizzards across northern China and Beijing seeing the first snowfall on November 6, 23 days earlier than average, a frigid winter could strain energy supplies."

Meanwhile Australia's eastern states are braced for a wetter than average summer, which could cause flooding and other disruption, the bank said.