News Release

Ontario Weather Review

April 2011

April 2011 will be remembered for its wet weather and perception of colder than normal temperatures.

Temperatures for most of the province were highly variable from one week to the next but, in the end, were within normal values. Most locations were within one degree of the normal mean temperature values. Moosonee was two degrees higher than temperatures expected for April.

Records for the most rainfall and total precipitation were broken this month at many locations, with some receiving between twice and close to four times the amount of rain normally expected in April. Records for the greatest amount of rainfall and precipitation were broken in Ottawa, Wiarton and Sault Ste Marie.

Single-day records were also broken during the month. A new daily record was set in Petawawa on April 10, when it received 25.8 millimetres of rain. On April 20, North Bay and Sudbury received 21.4 and 14.3 centimetres of snow respectively. The previous record amount of snow received that day in North Bay was 9.4 centimetres in 1948. Ottawa also broke its highest rainfall amount for April 26 with 20.6 millimetres of rain.

Overall, this past April was wetter-than-normal, with the exception of Trenton, which received less precipitation than normal. 

Severe Weather

This month heard the year’s first rumblings of severe thunderstorms, alongside winter-like weather, and ended with a large scale windstorm in the last days of the month. 

Ontario’s season for severe thunderstorms normally begins in mid-April, including storms capable of producing large hail, damaging winds, flooding rains and tornadoes. This year was no exception, as a combination of storm systems produced hail and damaging winds in various parts of the province. The first system moved into the west end of Lake Superior, from Minnesota, during the day on April 10 and produced golf-ball-sized hail in the Thunder Bay area. A second system of thunderstorms moved through south western and south central Ontario on April 10 and into Eastern Ontario during the early morning hours of April 11. Golf-ball-sized hail was reported in south western Ontario and heavy rain and localized damaging winds were reported in eastern Ontario.

Winter-like conditions prevailed throughout northern Ontario, as a low pressure system originating in Texas moved through north eastern Ontario on April 16 and into the morning on April 17. Areas across the North, from Sioux Lookout to Geraldton to Kapuskasing reported snowfall accumulations in the 20 to 30 centimetre range. Areas closer to Lake Superior and Lake Huron experienced a mixture of snow, ice pellets and freezing rain.

An intense storm system originating in the American Midwest generated a series of strong thunderstorms that marched across southern and eastern Ontario on April 27. A series of rainfall and freezing rain warnings were issued for central and north eastern Ontario. The thunderstorms in southern Ontario caused damage to trees, barns and some buildings in the Waterloo-Wellington, Dufferin and Simcoe County areas. Investigations are continuing as to whether some of this damage was caused by tornadoes.

The severe weather continued on April 28, as the centre of the storm moved up through Georgian Bay and into Quebec. The system spawned destructive winds in an area from southwest of Hamilton through the Niagara Peninsula, the Greater Toronto area and then eastwards through Peterborough and the Kawartha Lakes, and into Ottawa. Wind gusts measuring 85 to 100 kilometres per hour were common in these areas, with a peak gust of 124 kilometres per hour recorded just across the border at Niagara Falls, New York. There were numerous reports of trees being damaged or uprooted, power lines coming down and loose debris being blown about by the powerful winds. In fact, in the Grimsby area of the Niagara Peninsula a steel garage door that was leaning against a shed was picked up by a burst of wind and struck and killed a man.

Temperature and Precipitation Tables

Unusual mean temperature readings (in °C), ranked by variation from normal:

Location	Mean Temp	Normal	Difference	Warmest since
Moosonee	-0.4	-2.4	2.0	2010

 

Record rainfall readings (in mm), ranked by variation from normal:

Location	Rainfall	Normal	Difference	Previous Record
Ottawa	166.0	60.5	105.5	2005 (143.8)
Wiarton	159.2	54.9	104.3	1951 (136.4)
Sault Ste Marie	108.4	50.5	57.9	1947 (95.5)

 

Unusual rainfall readings (in mm), ranked by variation from normal:

Location	Rainfall	Normal	Difference	Most rain since
Elliot Lake	138.4	35.6	102.8	1960
Windsor	149.4	80.7	68.7	1947
Hamilton	136.0	69.6	66.4	2009
Sudbury	109.2	47.0	62.2	1981
North Bay	107.8	51.4	56.4	1981
Chapleau	59.5	24.1	35.4	2008
Toronto Pearson	93.4	62.4	31.0	2009

 

Unusual snowfall readings (in cm), ranked by variation from normal:

Location	Snowfall	Normal	Difference	Most snow since
Kapuskasing	65.2	28.1	37.1	1996

 

Unusual precipitation readings (in mm), ranked by variation from normal:

Location	Precipitation	Normal	Difference	Previous Record
Wiarton	165.9	68.1	97.8	1951 (155.4)
Ottawa	167.0	72.4	94.6	1993 (144.1)
Sault Ste Marie	122.3	68.5	53.8	1985 (121.1)

 

Table 1Unusual precipitation readings (in mm), ranked by variation from normal:

Location	Precipitation	Normal	Difference	Driest since / Wettest since
Trenton	45.2	77.1	-31.9	2010 (Driest since)
Elliot Lake	148.8	50.0	98.8	1960 (Wettest since)
Chapleau	117.1	46.3	70.8	2008 (Wettest since)
Windsor	155.4	85.1	70.3	1947 (Wettest since)
North Bay	133.4	67.2	66.2	1947 (Wettest since)
Hamilton	142.0	78.0	64.0	1996 (Wettest since)
Kingston	141.5	77.5	64.0	2000 (Wettest since)
Sudbury	126.2	64.9	61.3	1981 (Wettest since)
Kapuskasing	113.8	53.9	59.9	1981 (Wettest since)
Muskoka	126.4	78.9	47.5	1996 (Wettest since)
Wawa	109.4	62.9	46.5	2001 (Wettest since)
Kenora	72.5	32.7	39.8	2001 (Wettest since)
London	114.1	82.2	31.9	2009 (Wettest since)
Thunder Bay	71.6	41.5	30.1	2003 (Wettest since)
Moosonee	68.6	39.0	29.6	2009 (Wettest since)
Sarnia	103.9	75.4	28.5	2009 (Wettest since)
Toronto Pearson	96.6	68.4	28.2	2009 (Wettest since)

Note: The normal period used is the 1971-2000 Climate Normals

Media: For more information, please contact:

Laurie Thibeault
Communications Officer
Environment Canada – Ontario
905-336-4711