Toronto basked in mild temperatures this week in an unseasonably warm break from what has proven to be a brutally cold winter, but it didn't last long.

On Wednesday afternoon, Environment Canada issued a snowfall warning for the city, and with temperatures quickly sliding back below freezing, Toronto's Medical Officer of Health has added onto the warning, issuing yet another extreme cold weather alert (ECWA) Thursday morning.

The city reserves ECWAs for the coldest days, when temperatures are forecasted to dip to -15 C or colder, or when wind chill factors have it feeling like -20 C or colder, though other factors can contribute to these warnings being issued.

Typically, these alerts trigger the opening of the city's emergency warming centres at 7 p.m. on the day of the warning, though these facilities have remained open throughout the turbulent stretch of weather that has pummelled the city with frigid temperatures since Jan. 7.

Usually, the city keeps its warming centres open until noon on the day an alert is terminated, but this winter has been different. Thursday's warning is the third such alert issued in February alone, offering some explanation as to why the warming centres have remained open for well over one month now.

The city operates four warming centres covering different areas of the city, with a central location at 129 Peter St., one at 5800 Yonge St. in North York, another in the Better Living Centre at Exhibition Place, and at Scarborough Civic Centre.

Streets to Homes outreach staff will also be out trudging through what's expected to be up to 20 cm of snow to check in on vulnerable populations.

Like the warming centres, this program has been active continuously since Jan. 7, with teams urging those living outdoors to seek shelter, and offering blankets and winter clothing for those who choose to remain outside.

The city states that the ECWA will remain in effect until further notice.