Changes in the frequency of extreme temperature records for Toronto, Ontario, Canada

Temperature extremes in Toronto, Ontario, Canada are examined using an under-utilized approach. The frequency of temperature extreme records per year is examined for the period of 1971 to 2000. Consistent with other published metrics, record extreme cold temperatures is decreasing at five weather observing stations in the Greater Toronto Area. This was confirmed using three different statistical tests indicating the change signal was stronger for weather stations on the fringe of the urban area suggesting that expanding urbanization was a major factor in this net change. However, this was not found to be the case for record extreme warm temperatures where increasing trends were not statistically significant. The effects of the Mt. Pinatubo eruption in 1991 were detected in both the minimum and maximum temperatures records.