More than 40 days have passed since Vancouver's airport saw rain

The city recognized as one of the rainiest in Canada has gone more than 40 days without a single measurable drop, according to meteorologists.

Environment Canada said Vancouver International Airport last saw rain on June 15. The 41-day dry streak is expected to continue, putting the city on track to break a decades-old record.

The weather agency uses data from the airport to represent the Vancouver area.

"We're not seeing any precipitation on the horizon," said meteorologist Bobby Sekhon. "The next week or so still remains dry in Vancouver and even through the [B.C. Day] long weekend."

The months of July and August are usually dry in southern B.C. The difference this year is that the rain stopped weeks earlier than usual and didn't come back, Sekhon said.

"Given [the dry stretch] started in mid-June, that's the exceptional part," he said.

Trees and plants on the South Coast are generally well adapted to wet winters and springs followed by drier summers, according to forestry experts, but the extended dry period coupled with the record-breaking heatwave in late June has been taxing.

"Plants can survive on their stored energy for some time ... but in the longer run, those impacts can build up," said Sally Aitken, a professor of forestry at Vancouver's University of British Columbia.

Long-term effects

Lack of water affects plants in two different ways, Aitken explained. In the short-term, drought interferes with plants' ability to keep their existing cells alive. In the long run, they're unable to grow because they don't have enough water to absorb carbon dioxide as part of the photosynthesis process.

Many of the large conifer trees common in Vancouver, like the Douglas fir, are adapted to drought and "will be fine," according to Aitken. But she said trees growing in shallow soil, like those on rocky bluffs by the seaside, don't have the option of sending their roots deeper to find water and would be the "first to go."

Most of southern British Columbia is experiencing drought, as is the central Interior. Aitken said researchers have already seen some "die-back" among western red cedars and grand firs growing in shallow soil on eastern Vancouver Island.

Aitken said those findings are likely to become more common with climate change.

"There's a lot we don't know about how these forests are going to respond to climate change. But certainly, cumulative impacts are one of those," she said.

"We know that the trees in particular can withstand a lot of adversity throughout their lives. They have long lives. They're stuck in one place and they face multiple stresses during that lifetime."

"But if those stresses come piled on too quickly or these extreme years too frequently, we will likely see more and mortality."

Increased watering

The Vancouver Park Board has doubled down on its watering efforts by bringing in more watering trucks and extending staff hours.

Parks Commissioner Dave Demers says they are focusing on additional watering for young and isolated trees planted on downtown sidewalks which are the most vulnerable.

"We've seen downtown, after the heat dome, we've seen entire streets defoliate partially or fully," he said. "We've seen trees just go brown from the bottom to the top."

The park board is asking residents to help by watering trees near their property that appear to be in distress, either by letting a hose trickle or slowly pouring buckets of water near the trees' drip line — the outer edge of its foliage where roots absorb water the most efficiently.

Demers says while most trees will survive this dry season, the stress will affect them for years to come.

"Branches that were alive this year might just die next year. So the stress that our trees are living through now has impact that compounds over the years."

Dry streak likely to break record

The current dry spell could go on in the Vancouver area for several more weeks, Sekhon said. The all-time record for days without rain was set in 1951, when the city went rainless from June 14 to Aug. 10.

When the rains do come, the experts hope it will be thorough.

"We need a lot of precipitation to catch up and it doesn't look we're going to get a whole lot of it, at least not in the near term," the meteorologist said. "But we know as we get into September, October, that's when we start to get more of that rain cycle coming in."