Toronto is under its first extreme cold weather alert of the season, but if past weather is any indication, residents can expect several more before winter is over.

During the past decade, the city has had an average of 16 extreme cold weather alerts per year, compared to only one so far this year.

Based on the data from the past ten years, the majority of Toronto's extreme cold weather alerts fall in January and February.

The Medical Officer Health calls an extreme cold weather alert when Environment Canada forecasts that temperatures will reach -15 C or colder. Alerts are also issued at warmer temperatures if the forecast includes factors that increase the impact of cold weather on health.

Alerts can also be issued if there's a wind chill factor, precipitation or several days and nights of cold temperatures in a row.

Last year had the most extreme cold alerts in the past decade, with 36 alerts from December 2013 to March 2014.

The majority of extreme cold weather alerts tend to fall between January and February, with 80 per cent of instances recorded during the two month period.

Of 160 extreme cold alerts in the past 10 years, one was in November, 17 were in December, 19 were in March and two were in April.

During cold weather alerts, Toronto Medical Officer David McKeown advises residents to check up on loved ones and those who may be particularly vulnerable.

Groups at risk include the elderly, infants, people with pre-existing heart or respiratory conditions and the homeless.

During extremely cold weather, residents could face frostnip and frostbite, hypothermia and heart conditions.

To stay warm, residents should dress in layers covering all exposed skin, stay dry, seek shelter and avoid drinking alcohol.