The tragic events of Sept. 11, 2001 presented a unique opportunity to examine the anthropogenic effects on climate due to severe flight restrictions over much of North America. An earlier study for the continental U.S. found the daily temperature range (DTR) for Sept. 11-14 was 1.8 C higher than for the adjacent three-day periods (D. J. Travis et al, Nature, Vol. 418, 601 (2002)). It was suggested that the lack of airplane contrails was in part responsible for this change. This study examined hourly measurements of temperature, relative humidity and temperature as well as daily observations of precipitation recorded at airport stations in Canada for the period Sept. 8-17, 2001. These data were then compared to data archived by Environment Canada taken during 1977-2004. This period of time was selected as it is relatively unaffected by changes in instruments and data taking procedures (W. A. van Wijngaarden & L. A. Vincent, Geophysical Research, Vol. 110, D22102 (2005)). The results are examined as a function of latitude and geographical proximity to regions in the U.S. where conditions for contrail formation are most favourable.