'Rex Block' keeps things dry as local firefighters call for caution on outdoor burns

A weather phenomenon known as a Rex Block helped make for a very arid month of May in southwestern Ontario, with firefighters in the London area keeping a close eye on the fire threat while considering an outdoor burning ban. 

According to CBC's climate dashboard, which you can use here, the maximum temperature over the next few days will be about 32 C, which is 10 C above average. 

That will follow what was a very dry May. 

Monica Vaswani is a meteorologist for Environment Canada. She said the Rex Block is a mass of high-pressure air that essentially stops other weather systems from blowing in. Right now, a Rex Block is pretty much parked over southwestern Ontario. 

"We've only seen about five per cent of what you would normally see in terms of rainfall for the entire month of May," she said. "It's pretty unusual." 

Vaswani said a normal rainfall amount for May would be about 89.4 mm. However only 4.1 mm of rain fell in May. It's not a record, but certainly conditions are still unusually dry. 

There is a chance of some rain over the weekend in the London region, with forecasts calling for a 40 per cent chance on Saturday and a 30 per cent chance on Monday. 

Temperature are also expected to dip as the weekend wraps up, with highs on Sunday and early next week expected to be in the mid-20s. 

But until the rain comes, firefighters will continue to keep a close eye on the fire threat. 

Natural Resources Canada has an "extreme" fire danger rating in place for most of southern Ontario at a time when Alberta and Nova Scotia are dealing with stubborn forest fires. 

Ron De Brouwer is the fire chief for Lucan Buddulph. He holds regular discussions with other Middlesex County fire chiefs. He said for now, they've decided a complete ban on outdoor burning isn't needed. However he also said one will likely be put in place if the dry conditions continue. 

"We're not in a crisis position yet," he said. 

Each municipality has its own outdoor burning rules, which property owners should consult before doing any burning. In Lucan, any fire with a flame higher than three feet requires a burning permit. If a burn ban is put in place, no permits will be issued across Middlesex County, said De Brouwer.

On Thursday, firefighters were called to a barn fire at a horse stable just west of London in the rural community of Delaware. The cause of the fire is under investigation and there's nothing to suggest it was caused by the warm weather.