Good to moderate air quality expected

Weather Summary: Issued on Thursday, May 15, 2008

A high pressure ridge over the central Great Lakes region during Thursday is causing skies to become sunny and causing northwesterly winds, diminishing over most regions, but persisting over eastern regions during most of the day.

During Friday, a weak weather pattern is expected to result from the weakening ridge over central and northeastern Ontario, a southern low pressure region south of the eastern Great Lakes spreading some cloudiness over southwestern Ontario, and a northern low pressure trough spreading cloudiness over northwestern regions.

During Saturday, a northern low pressure system is forecast to move southeastward across Ontario, spreading cloudiness and scattered precipitation over most regions.

During Thursday, air quality indices are forecast to be in the good to moderate categories in most regions due to ozone, except generally in the good category in eastern Ontario with northwesterly winds during most of the day. During Friday, air quality indices are forecast to be in the good to moderate categories in most regions due to ozone, except generally in the good category in northwestern regions where skies become mostly cloudy. During Saturday, air quality indices are forecast to be mostly in the good category under cloudy skies except for possible indices in the moderate category in southwestern regions where skies may be partly sunny during the afternoon.

Smog Alert by Email

Sign up now to receive notification of Smog Alerts

Smog, comprised of ozone and/or PM_2.5, is primarily a summer phenomenon, occurring mostly in southern Ontario; however, PM_2.5 can elevate smog levels during all months of the year. For this reason, the ministry reports the AQI hourly, seven days a week; and continues to provide air quality forecasts daily.