An extreme cold weather alert has been issued for Toronto, as temperatures are expected to drop into the negative double digits overnight. 

Environment Canada says the overnight temperature will hit –12 C, though strong winds gusting at up to 40 km/h will make it feel much colder. 

Toronto's Medical Officer of Health,  Dr. David McKeown, issued the alert Sunday morning, and says it will stay in effect until further notice. 

Residents are encouraged to dress in warm layers and to call or visit friends, neighbours and family who might be having trouble with the cold weather. Infants and young children, the homeless, people who work outdoors and those with heart or respiratory illnesses are among those at risk, officials say. 

During such alerts extra effort is made to help homeless people to get off the street and into shelters. From Jan. 1 to Feb. 29, the city funds two drop-in centres that are open 24 hours.

If you see someone on the street who needs help with the cold call 311 or, for medical emergencies, 911.