Environment Canada
www.ec.gc.ca
Ontario Weather Review
September 2014
The month of September took Ontarians on a roller coaster of seasons, offering summerlike temperatures, colourful foliage display and snow!
This might surprise many readers, but this past month was normal in terms of overall mean
temperatures across the province. Some may remember the warm conditions of the
beginning of the month (for 10 days or so) and the last week of the month. Others may
focus on the cooler days, with night-time freezing temperatures and snow – in places like
Chapleau, Wawa, Sioux Lookout and Geraldton, to name a few locations. Overall, though,
the warmer and cooler periods balanced each other out, meaning mean temperatures
across the province were within the normal range for the month. The largest departures
from normal values – yet still within the 2 degrees Celsius threshold – were observed in
Eastern Ontario, where temperatures were slightly warmer than normal, and in Windsor,
where it was the coolest September since 1995.
Wetter-than-normal conditions were reported in the southwest, northeast and North of
Superior. Precipitation amounts in those locations ranged from 1¼ times to more than
double the amount expected for September. In Kitchener-Waterloo, it was the second
wettest September since 1970. Precipitation was within the normal range elsewhere,
except for a few locations where conditions were drier than normal.
Severe Weather
The month of September was relatively quiet in Ontario except on a few days. Of these,
September 5 was the most significant.
That day, severe thunderstorms affected parts of south, central and eastern Ontario. In the
morning, lightning from a thunderstorm complex west of Toronto was responsible for a
fatality at the University of Waterloo. Then around 2 p.m., a few thunderstorms crossed
southern Georgian Bay and Lake Simcoe and were responsible for damage on Christian
Island – which was later deemed to be from an EF0 tornado, with winds of at least 90
km/hr – as well as downburst damage near Port Severn. Another thunderstorm in the warm
air mass that afternoon caused rainfall of up to 60 mm and also local tree damage in the
Ottawa-to-Renfrew area. Later that afternoon and into the evening hours, a stronger line of
thunderstorms crossed Lake Huron, Georgian Bay and then much of southern Ontario.
Downburst damage occurred in Orillia and one tornado was confirmed in Ramara
Township east of Orillia. It was rated an EF1 tornado, with maximum winds of 115 km/hr.
Meanwhile, as the thunderstorms crossed the rest of southern Ontario, significant rainfall
amounts were observed in many locations – as high as 125 mm in St. Thomas, where
there was local flooding. Strong winds from localized downbursts were also reported in
London and Windsor. The same downburst that affected Windsor with 50-knot winds
forced an evacuation of the WineFest event in Amherstburg that evening.
September 10 was also a busy weather day across the province of Ontario. A low-pressure
system moving eastward across northern Lake Michigan and Manitoulin Island brought
southerly winds, a warm air mass and heavy rainfall to many parts of southern Ontario.
North of this system’s track, heavy rainfall occurred in conjunction with northeasterly winds
and a very cool air mass. Over both areas, general rainfalls of 40 to 60 mm were observed.
In southern Ontario, the maximum was 100 mm in Amherstburg and 69 mm in London,
while over northeastern Ontario the maximum of 74 mm was recorded in Timmins.
On September 19 and 20, a low-pressure system crossing northern Ontario brought rain to
most areas. Many locations reported rainfall amounts between 20 and 40 mm. Geraldton,
however, reported a two-day total of 84 mm.
Finally, on September 21, localized flooding and road washouts were reported in the
Seguin Township area, near Parry Sound, as a result of some heavy rainfalls that occurred
near midday. While surface reports only confirm 33 mm at Parry Sound, radar estimates
suggest that upwards of 100 mm could have occurred in a few areas.
Unusual precipitation readings (in mm), ranked by variation from normal:
Location
Kitchener/Waterloo
London
Timmins
Geraldton
Kapuskasing
Windsor
Chapleau
Wawa
Toronto Pearson
Sarnia
Precipitation
179.0
165.0
142.5
159.2
142.8
135.0
126.8
152.8
102.8
131.7
Normal Difference
87.8
91.2
103.0
62.0
84.7
57.8
101.6
57.6
100.9
41.9
93.9
41.1
95.1
31.7
122.0
30.8
74.5
28.3
104.7
27.0
Wettest since
1986
2006
2002
2010
2010
2011
2010
2010
2012
2008
Location
Precipitation Normal Difference
Driest since
Kingston
32.1
95.4
-63.3
2007
Trenton
51.8
90.1
-38.3
2007
Thunder Bay *
55.8
88.0
-32.2
2012
* Climate Normals for the period 1971-2000. The 1981-2010 normals are used for all other
stations.
Media: For more information, please contact:
Geoff Coulson
Warning Preparedness Meteorologist
Environment Canada
416-739-4466
(Également offert en français)