JULY DEFINITELY WARMER, AND HOW ABOUT THAT HUMIDEX?

Mark Clairmont | MuskokaTODAY.com

If you thought July was hotter than the start of August, you were right.

But only slightly.

However, when you factor in the humidex, ask the folks in Sarnia.

On July 19 — remember that day — it was a whopping 47 Celsius with the humidity.

And in Muskoka the end the month went out with a bit of a bang on July 29-30 when winds picked up in Gravenhurst and areas west of Bracebridge, where trees and power lines came down onto cottages and blocked roads.

Meanwhile, according to the Ontario Weather Review for last month, temperatures in July 2019 reversed the normal or cooler-than-normal trend Ontarians have been under since January.

In July, mean temperatures were finally warmer than normal by 1 to 3°C.

Peter Kimbell, environmental climatologist with Environment and Climate Change Canada, says that uring the month there were just three short-lived heat episodes, at the start, middle and end of the month — from July 3-6, 16-20th and 27-29th.

On July 19th, the humidex made it feel like 47 in Sarnia, while on July 20th, humidex values in the mid forties were reported in Ottawa (46), Windsor (46) and Toronto (44).

Kimbell said rain for most of Northwestern Ontario contrasted with that of previous months. Most of the Northwest received above-normal precipitation amounts; anomalies ranging from normal to twice the expected amounts.

However, this is not representative of the precipitation patterns for most of the province as north of Superior, the Northeast and Southern Ontario received well below normal precipitation amounts, with anomalies of -25 to -75%.

Despite the small monthly totals for most of the province, some single-day rainfall amounts are worth mentioning, such as 67.0 mm received on July 17th at Toronto’s Pearson Airport from thunderstorms and rain showers.

Observations compared to the 1981-2010 normals for July 2019 (see Appendix for a geographic representation of all of Ontario) City	Mean Temp (obs/normal) (°C)	Difference (°C)	Total Precip (obs/normal) (mm)
Kenora	20.2 / 19.7	0.5	155.5 / 103.4
Moosonee	17.4 / 15.8	1.6	41.0 / 96.8
OttawaAirport	22.3 / 21.0	1.3	52.1 / 91.9
Sudbury	19.9 / 19.1	0.8	86.8 / 76.9
Thunder Bay1	19.2 / 17.6	1.6	96.4 / 89.0
Toronto Pearson	23.4 / 21.5	1.9	104.2 / 75.7
Windsor	25.1 / 23.0	2.1	93.5 / 89.2

 

*estimated or incomplete value

1 1971-2000 normals used

Significant Events

July 10: Awash in Rain in Northwestern Ontario

Heavy downpours from thunderstorms gave whopping rainfall of 110 mm in three hours to Vermilion Bay; nearly 200 mm fell there in total within a 24-hour period. Multiple roads were washed out in the area, including parts of Highways 17, 105, 594, and 609.

July 15: Strong winds in the Northwest

A line of severe thunderstorms affected many areas in the northwestern part of the province. Wind gusts of up to 85 km/h caused tree damage in Fort Frances and Quetico Provincial Park. There were some power outages in Fort Frances and Thunder Bay. Farther north, minor roof damage and downed trees were reported in the Mishkeegogamang Ojibway First Nation, south of Pickle Lake.

July 17: Heavy Rain in the Southern Ontario

Many southern Ontarians woke up to heavy rain. In particular, the heaviest amounts of rain were in west Toronto with a report of 104 mm in three hours. Many parts of the city saw flooding including a section of Highway 401 east of Highway 427 and one of its off-ramps where a car became stuck with water flooded up to its windows. Many flooded roadways in Toronto resulted in major traffic delays. Even the Toronto Transit Commission had to close one of its stations for two hours due to flooding. High amounts of rainfall were not just limited to Toronto; areas between Bowmanville and Cobourg received 70 to 100 mm.

July 19: Hail and Wind in the Southwest and the Golden Horseshoe

Severe thunderstorms moved through southwestern Ontario and the Golden Horseshoe. In particular, they brought nickel- and golf ball-sized hail and localized flooding to London. Lightning struck a tree in the east part of the city, which then split, sending wood and debris around the neighbourhood into pools and onto rooftops. Tree damage was reported in Caledonia, Dunnville, Burlington, with a trailer flipped ono its side in Caledonia.

July 20: Thunderstorms Surges onto Ontario’s Lake Huron Shores

Another stormy day in southwestern Ontario as thunderstorms moved through the area. With gusts of 94 km/h reported in Windsor and 83 km/h in Kitchener, the storms caused downed trees and downed power lines with more than 12,000 customers without power. From Grand Bend to Lambton Shores, including Pinery Provincial Park, the strong winds from the thunderstorms led to rising water levels along the shores of Lake Huron; flooding ensued and recycling bins were seen floating in the water in Grand Bend. Metal roof tiles were sent flying due to the gusty conditions.

July 26: Stormy Day for Northwestern Ontario

Severe thunderstorms developed east of Fort Frances and moved along the Trans-Canada Highway towards Thunder Bay. The most significant damage seemed to have occurred between Atikokan and Shebandowan. In Atikokan, the storms brought several downed trees and quarter-sized hail, whereas farther east near Quetico College, a witness noted possibly hundreds of trees were damaged in the area. Minor power outages resulted and marble-sized hail was observed in the area. While most of the wind damage was likely caused by a downburst near Quetico College, in an area just slightly west of it and north of Crystal Lake, high resolution satellite imagery suggests that an EF1 tornado had occurred. Investigation is still on-going at the time of publication.

July 29 – 30: Thunderstorms

The southern half of the province endured another day of active weather. In the East just southwest of Pembroke in the down of Deacon, many 100-year-old trees were uprooted and fell on cottages due to strong winds from thunderstorms damaging 10 to 20 houses. Similarly, in areas west of Bracebridge, trees and power lines came down onto cottages and blocked roads. Thunderstorms also brought torrential rain and gusty conditions to areas near Barrie.

A cold front associated with the system triggered more thunderstorms in eastern Ontario on the 30th. Many reports were received from Cornwall of uprooted trees and snapped branches on roads, buildings, and cars, as well as downed signs and fences.

Forest Fires Update

Smoke from a forest fire threatened the Keewaywin First Nation (FN). It declared an emergency on July 1. Evacuations took place for nearly 400 people from the community. On July 6, Pikangikum also decided to evacuate their vulnerable community members due to smoke impacts. Nearly 2500 people were sent to host communities, some even to Regina, Saskatchewan. As smoke no longer affected the communities later in the month, most evacuees from both Keewaywin and Pikangikum FNs had returned home by July 21.

High Water Levels over the Lower Great Lakes

Many conservation authorities along shores of the lower Great Lakes maintained their flood messages by the end of the month due to high water levels. Although Lakes Ontario and Erie’s water levels have been declining, weather systems could still generate sustained onshore winds resulting in storm surge. Shoreline erosion due to damaging waves and localized flooding is still a cause of concern as August begins.

Outlook for August

Temperatures are forecast to be near normal for the province for the month. For the next two weeks, precipitation seems to be near normal for the South, and range from near-normal to somewhat above-normal in the North. No clear signal is present thereafter.