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Ontario Weather Review - May 2008
After a long, cold winter, summer-like temperatures were highly anticipated for May, but they failed to make an appearance. The cool temperatures of the past few months continued, with values in some cases four to five degrees below normal.
Northwestern Ontario in particular has been blocked from most of the warm weather experienced even sporadically through other parts of the province. Snow and frost were reported across most of Northern and Central Ontario right into the last week of the month. Southern Ontario was also cooler than normal, with most location reporting values one to two degrees below normal.
Precipitation was variable through the province. Some storms produced single- day high rainfall amounts, bringing those monthly totals to well above average. Ontario had a number of reports of 15 to 30 millimetres recorded on May 7, 30 and 31. Otherwise, some sites reported near-normal to below-normal values.
Severe Weather
The summer severe weather season usually begins in Ontario in late April, with severe thunderstorms producing damaging winds, large hail, torrential rains and tornadoes. However, this month was conspicuous by its almost total lack of damaging thunderstorms or tornadoes. There are usually one or two events in late April, followed by a few notable events across the province in May, but the season this year has been very slow to get going. The same cannot be said for the United States, where large numbers of deadly tornadoes have been occurring across the U.S. Midwest and Deep South over the past few weeks.
That being said, the first two confirmed tornadoes of the season did occur on May 26 in Central Ontario. At approximately 4:40 PM, a tornado was spotted in Windy Lake Provincial Park to the northwest of Sudbury, followed by a second tornado that occurred in the Redbridge area to the northeast of North Bay. Neither tornado caused significant damage. Both were rated as Fujita Scale Zero tornadoes, with peak winds approaching 115 kilometres per hour. The Fujita Scale goes from F0 (weakest) to F5 (strongest), where Fujita Scale 5 storms can have winds approaching 500 kilometres per hour. There has never been a confirmed F5 tornado in Ontario. Canada's first confirmed F5 tornado occurred last June in Elie, Manitoba, to the west of Winnipeg.
These first confirmed tornadoes of 2008 acted as a reminder that we are now well into the summer severe weather season in Ontario. Severe thunderstorms that can bring damaging winds, large hail, flooding rains and tornadoes usually occur between late April and early October in this province. The average number of confirmed and probable tornadoes in Ontario based on the last 25 years worth of data is 11. Last year, there were nine.
Unusual temperature readings:
| Location |
Mean temp |
Normal |
Difference |
Warmest since |
| Pickle Lake |
4.8 |
9.3 |
-4.5 |
2004 |
| Dryden |
7.1 |
11.2 |
-4.1 |
2004 |
| Kenora |
8.1 |
11.8 |
-3.7 |
2004 |
| Sioux Lookout |
7 |
10.5 |
-3.5 |
2004 |
| Red Lake |
6.6 |
10 |
-3.4 |
2004 |
| Geraldton |
5.8 |
8.5 |
-2.7 |
2004 |
| Muskoka |
9 |
11.5 |
-2.5 |
2002 |
| Wawa |
5.8 |
8.2 |
-2.4 |
2002 |
| Sault Ste Marie |
7.7 |
10 |
-2.3 |
2002 |
| Waterloo Wellington |
10.2 |
12.5 |
-2.3 |
2005 |
| Chapleau |
7.2 |
9.4 |
-2.2 |
2002 |
| Petawawa |
9.7 |
11.9 |
-2.2 |
2002 |
| Thunder Bay |
7.4 |
9.5 |
-2.1 |
2004 |
| Sudbury |
9.3 |
11.3 |
-2 |
2002 |
| Elliot Lake |
9.2 |
11.2 |
-2 |
2004 |
| Timmins |
7.6 |
9.6 |
-2 |
2004 |
Unusual precipitation readings (in millimetres):
| Location |
Precipitation |
Normal |
Difference |
Wettest since |
| Wiarton |
137.5 |
75.3 |
62.2 |
2004 |
| Moosonee |
113.4 |
53.7 |
59.7 |
1999 |
| Timmins |
121.3 |
69.2 |
52.1 |
1960 |
| North Bay |
134.4 |
87.6 |
46.8 |
2004 |
| Trenton |
115.1 |
71.6 |
43.5 |
2003 |
| Kapuskasing |
109.6 |
66.3 |
43.3 |
2007 |
| Chapleau |
112.6 |
72.7 |
39.9 |
1993 |
| Petawawa |
106.4 |
68.5 |
37.9 |
2004 |
| Pickle Lake |
92.8 |
60.3 |
32.5 |
2007 |
| Geraldton |
98.6 |
69.1 |
29.5 |
2007 |
| Thunder Bay |
95.6 |
66.5 |
29.1 |
2006 |
| Muskoka |
117 |
91.1 |
25.9 |
2004 |
| Earlton |
92 |
67 |
25 |
2001 |
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