Is flash flooding more frequent in the Maritimes this summer?

It's been a summer of weather extremes here in the Maritimes.

The dry weather and devastating wildfires began things in May, but since then it's been heat, humidity and flooding.

The heavy rainfall of early June in western Nova Scotia kicked off the wet weather pattern, when 100 mm to 180 mm of rain fell over just a few days.

The Edmundston, N.B., area was then hit with damaging flash flooding in late June when more than 50 mm of rain fell in just a few hours.

Then, of course, there was the historic flood in late July which dropped more than 250 mm of rain on parts of Nova Scotia.

It was followed by a fourth extreme rainfall just two weeks later, which caused flooding in Halifax and Dartmouth, N.S., over the weekend.

So are flash-flooding events occurring more frequently in the Maritimes this summer?

Unfortunately, there was a lack of widespread private weather stations, no social media and the world was less connected in years past, which means these locally heavy rainfall events could easily have been missed by the record books.

Given that, we just can't say with certainty that we are seeing a historic number of extreme rainfall events this year in the Maritimes.

However, thanks to our friends just across the border, we can say that this year is very likely one of the highest for flash flooding in the region over the past few decades.

The National Weather Service in the northeast U.S. issued a record number of flash-flood warnings in the month of July. 

While records only go back to 1988, it does confirm that this year has certainly been active in the region. Both Maine and New Hampshire have already issued more warnings than in any other calendar year.

The high number of flash-flood warnings south of the border further highlights how there is no similar national system in Canada.

While we can see that thunderstorms are going to be present days in advance, given the convective nature of these small-scale systems, they simply aren't handled well by forecast model guidance. This limits the lead time for assessing how severe the thunderstorms may become and where exactly they will hit.

As a result, it often takes real-time analysis using satellite and radar imagery as the storms move into the area.

With no ability to issue flash-flood warnings, Environment Canada can only issue rainfall warnings, the same way it would with any other event dropping 25 mm in one hour, 50 mm in 24 hours, or 75 mm in 48 hours.

Why is this year different?

Record heat and humidity in the region in the month of July meant there was both plenty of energy and moisture in the atmosphere.

Thunderstorms that hit the region have ample fuel and we've now seen multiple events where storms "train" through the region, pouring heavy rain over the same area. Saturday was yet another example of that in the Halifax and Truro, N.S., areas. 

Warm sea-surface temperatures could also be a factor, however more research will be needed to say definitively that it's having an impact.

Climate scientists are always quick to point out that you can't point to any single event and say it was caused by climate change.

However, they have also repeatedly warned of more extreme weather in a warming world.

More thunderstorms to watch

We aren't in the clear yet.

Another front is crossing the Maritimes Tuesday and Wednesday with more heavy rainfall and the potential for more flash flooding. While the greatest risk for localized flooding will be in New Brunswick, the risk of heavy downpours and thunderstorms is there for Nova Scotia as well.

Yet another heavy rain looks set for Friday. While it's still early, this event also looks like one to watch for flash-flooding potential.

Stay tuned to CBC radio, TV, online and my social media feeds in the coming days.