Climate Change Chart of Ottawa, Canada

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +1.09 °C compared with the earlier reference period; this is an unweighted comparison of monthly means, not a day-weighted annual figure or a measure of daytime maximum temperatures. The largest monthly increase was in December, with a difference of +3.10 °C. By contrast, November had the largest monthly decrease, a difference of -0.55 °C; these month-specific changes show that the average shift was not uniform across the calendar.

Changes in snowfall

Averaged across calendar months, mean daily snowfall had a difference of -0.46 mm/day compared with the earlier reference period. This is an unweighted comparison of monthly means, and the daily measure should not be read as a monthly snowfall total. The largest monthly decrease was recorded in March, with a difference of -2.71 mm/day, while February had the largest monthly increase, at a difference of +1.27 mm/day. These month-specific differences indicate contrasting changes rather than a uniform shift across the calendar.

Changes in sunshine duration

Mean daily sunshine duration, averaged across calendar months, had a difference of -0.28 hours/day compared with the earlier reference period. This is an unweighted average of monthly means, not a day-weighted annual measure. The largest monthly decrease was in April, with a difference of -0.91 hours/day; the largest monthly increase occurred in May, at a difference of +0.78 hours/day. The opposite directions across these months show why the overall mean should not be taken to describe every month individually.

Changes in rainfall

Averaged across calendar months, mean daily rainfall had a difference of +0.29 mm/day compared with the earlier reference period. This is based on unweighted monthly means and describes daily rainfall averages rather than monthly totals. The largest monthly increase occurred in April, with a difference of +0.92 mm/day, while the largest monthly decrease was in May, at a difference of -0.67 mm/day. These contrasting monthly differences qualify the overall mean and do not imply the same change in every month.