Tropical temperatures in Winnipeg briefly shut down Assiniboine Park's hothouse

Winnipeg's balmy weather was a little too tropical over the weekend for even Assiniboine Park's tropical biomes at the Leaf.

The new indoor horticultural attraction, which opened in December and features four biomes, was shut down to the public on Sunday when a sensor inside the tropical biome recorded a reading of 43 C around 11:45 a.m.

"[That] triggered a decision to temporarily close out of an abundance of caution and concern for visitors, staff and volunteers," said Laura Cabak, director of communications for Assiniboine Park Conservancy.

The temperature in Winnipeg peaked at 32 C around noon that day, but the humidity in the air made it feel more like 38, Environment Canada said.

The attraction was closed for about three hours, until the weather cooled significantly, with a temperature drop of about nine degrees.

In summer, temperatures inside the biomes are regulated using evaporative cooling, such as misting, as well as natural fresh air ventilation, but the ability to cool the biomes is limited by the outside air temperature, Cabak said.

"These temperature regulation measures were certainly put to the test," she said.

The sensor with the high reading had been sitting in a beam of direct sunlight.

When they later checked the data from Sunday, the average peak temperature of readings taken from multiple sensors in various locations in the biome was closer to 33.7 C, and it was similar in the neighbouring Mediterranean biome, Cabak said.

Although still a sweaty level, it's within the Leaf's operating range. Air temperature in the biomes is typically between 25 C and 36 C depending on the time of day, season, sunlight and weather outside, she said.

By the time the Leaf reopened for the remainder of the day, the direct afternoon sun had shifted away, Cabak said.

"As we are within our first year of operations, we are still learning how the building responds to changing weather conditions and how best to manage that using the available environmental control systems," Cabak said.

Protocols will be adjust when and if needed to maintain temperatures in the desired range "to the best of our ability," she said.

"While we don't expect heat related closures to be a regular occurrence, we are prepared to temporarily close as a safety precaution if necessary."

Cabak wasn't sure how many people the closure impacted.

Aside from those who were inside and had to leave, there were others with tickets for scheduled visiting times. They were sent email alerts about the situation, she said.

"We went out about six hours [for those with booked times] because we weren't sure, of course, how long we might be closed."

Environment Canada's forecast for the rest of the week shows a return to more normal temperatures in Winnipeg before another spike into the 30s for the latter part of the weekend and into the start of next week.

Normal temperatures for this time of year are a high of 23 C and overnight low of 10 C.