A flash flood on Monday, July 4 caused roads like Main Street to flood in Penticton. (Dora Nelson Facebook)

A flash flood on Monday, July 4 caused roads like Main Street to flood in Penticton. (Dora Nelson Facebook)

‘1 in 10-year event’: Experts react to severe flash rain events in the Okanagan

‘We’re not out of the woods yet. There’s another storm coming on Thursday,’ says Doug Lundquist

Monday afternoon’s rainfall in the Okanagan was so significant that meteorologists say such an event may not happen for at least another 10 years.

Within 45 minutes between 2 p.m. to 3 p.m. on July 4, more than 12 millimetres of rain fell to the ground in Penticton, prompting the evacuation of 16 homes, 86 structures flooded and the activation of a local state of emergency.

But Environment Canada meteorologist Doug Lundquist says the focus of the event should be more on the “return rate” of the rain, as opposed to overall precipitation statistics.

“All the way from the U.S. border at Osoyoos and to the suburbs of Kelowna, there were storms that recorded a return rate of 10 years, at the minimum,” he explained. “That’s just based on where our weather stations are, though. In all likelihood, the return period is probably even longer than that.”

Though it was Penticton’s emergency operations centre who responded to 86 flood-related calls from residents on Monday, Lundquist says that Summerland actually experienced the heaviest rainfall in the South Okanagan.

Based on the location of the local Environment Canada weather centre, Summerland set its own all-time precipitation record for the day of July 4, experiencing more than eight millimetres of rain in one hour with 15.7 mm in total.

Lundquist added that Osoyoos also broke its own daily precipitation record on Monday (14.1 mm).

While Penticton fell short of setting a daily record, what set the city apart compared to other Okanagan communities was the number of different neighbourhoods that were affected by the heavy amounts of rain.

“What’s unique about this is for Penticton that the most severe weather hit right where people live,” Lundquist said. “There have been storms like this in the high terrain, which is why Mission Creek in Kelowna has peaked out a couple of times in the last month or so.

“But we haven’t seen something like that this year and it seems as though it affected people in Penticton the most.”

Before the anticipated heatwave next week — where temperatures are expected to reach up to 32 C — Lundquist says that people in the Okanagan should still be on guard for severe storms until Thursday.

“We’re not out of the woods just yet,” he said. “‘There’s another storm that may be coming on Thursday, and we’re worried about that, too.”

READ MORE: Okanagan summer heat is a week away

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