It's always encouraging when someone finds one of these blog posts helpful so I was pleased when the editor of the OGS Weekly eNews saw fit to reproduce the post of Daily Temperatures from the St. Lawrence River Valley in last weekend's edition. That source gives historic daily temperatures for Quebec City - Montreal and adjacent areas. As you move further away it will be less valid. I wouldn't want to trust it for Toronto daily temperatures.
Toronto has the first official daily weather records in Ontario, starting in March 1840. They were taken at a site near Varsity Stadium at 299 Bloor St W. Before official records there's the diary of Rev. Charles Dade, head of mathematics at Upper Canada College, then not far from Fort York. He took readings usually two or three times a day from January 1831 to April 1841. There is a gap from October 1838 to June 1839 when Dade returned to England, he was a native of Great Yarmouth, Norfolk, for the winter. Images of the diary up to that gap are online at http://heritage.canadiana.ca/view/oocihm.lac_reel_c9164/631?r=0&s=3. The meteorological part of the journal, which gives daily wind direction and a bried description of conditions as well as temperatures, starts with 1 January 1831, image 392, and ends with image 634 for June 1837. Unfortunately it stops short of the rebellion of December 1837.
R. B. Crowe's Reconstruction of Toronto Temperatures 1778-1840 Using Various United States and Other Data (pdf) using Dade's and other records appends a tabulation of monthly mean temperature estimates to 1989. The coldest year in that record is 1875, with February being particularly bitter. It was so cold from the 4th to the 19th that the Toronto Observatory issued a special memorandum, reprinted in the Globe, commenting it was twice as long a period of bitter cold as previously recorded, and colder. That year is one of the coldest in not only the St Lawrence record but as far afield as Boston and Chicago.