Ottawa's wettest summer on record: 488 millimetres and counting through August

Ottawa has officially recorded its wettest summer since rainfall tracking began in 1872. Through August 10, the city received 488 millimetres of rain — surpassing the previous record of 464 millimetres set in 1972.

Retired climatologist David Phillips, who analyzed data from Ottawa International Airport, said the deluge reflects a pattern of intense, short-duration storms rather than sustained rainfall. In July alone, 281 millimetres fell — nearly three times the typical 88 millimetres for that month. June brought 123 millimetres against an average of 97. As of mid-August, the city had already received 83 millimetres when the seasonal normal is about 25.

"We're just adding to that record almost daily," Phillips said, noting that with 21 days remaining in August, the summer total will almost certainly climb higher.

The intense rainfall has outpaced the city's infrastructure. When precipitation falls heavily in a single hour rather than spread across eight hours, flooding intensifies — something Ottawa's sewer system wasn't designed to handle. The Canada Day storm on July 1 exemplified this extreme weather event, contributing to the record-breaking month.

Montreal and Toronto have also experienced wetter-than-normal summers — Montreal about 40 per cent above average, Toronto about 18 per cent. Phillips cautioned that extreme weather patterns don't guarantee next summer will repeat: "Next year might be the driest on record. It's more extreme, but it's also more variable."

The wettest summer comes as the O-Train west extension grapples with flood damage from the July 1 storm, with months of construction work undone at Moodie Station.