Extreme rain in Nova Scotia exceeds once-in-a-century event

A submerged car is seen in this July 21, 2023, photo.

Environment and Climate Change Canada (ECCC) is working on analyzing data from the flooding rain in Nova Scotia in the context of past historical events.

CTV News spoke with the governmental agency on the data that they have so far.

According to the data the organization has for Halifax International Airport and surrounding areas, a one-in-a-hundred-year daily rainfall would be about 172 mm. A one-in-a-hundred-year event is defined as an event that will be equalled or exceeded on average once every 100 years.

Reports from this event in that area had totals exceeding 200 mm.

“Safe to say this is more than a one-in-a-hundred-year rain event,” noted Bob Robichaud, Warning Prepardness Meteorologist with ECCC.

As for rainfall rates, the storm peaked at a recorded near 40 mm in one hour, which according to Robichaud, is a one-in-ten-year event. That means that the extreme rainfall rates seen with this storm can be expected to occur more frequently than the extreme totals. He noted that the Thanksgiving Day flood in October of 2016 in Cape Breton also a recorded rain rate of 40 mm in one hour.

CTV News asked Robichaud if, given climate change, could these events become more frequent. He noted that one of more assured outcomes of a warmer climate is more extreme rainfall events and a higher frequency of occurrence. He added that just a few weeks ago, a similar event was seen in the state of Vermont.

“We are seeing more of them,” said Robichaud. “We won’t necessarily see them all happen here in the Maritimes, but we are seeing a higher frequency of these events.”