There are two ways to see a hawk owl, neither with great odds in any given short time period. Go where they are regular or wait for a report of one further south. Look at ebird, up on Highway 11 around Mattice in Feb or March you might be able to spot one if you drive around a lot. The place some people go who really want to see one in a given year is Sax-Zim bog near Duluth, Minnesota, or in Manitoba. In southern Ontario, they are rare enough that I don't think actively searching is worthwhile, they are not here every year or anything close to it, or in any particular area. Best to monitor ebird and/or Ontbirds for a sighting. Fortunately when one is found it usually sticks around for a while.