Good to moderate air quality expected

Weather Summary: Issued on Tuesday, March 9, 2010

A high pressure ridge over southern Ontario during Tuesday is causing mostly sunny skies and light winds over most regions except for some cloudiness over northwestern regions. Winds are forecast to be northwesterly over eastern and northeastern Ontario regions and southerly over southern and northwestern regions west of the ridge. Temperatures are forecast to continue warmer than seasonal values.

During Wednesday, the ridge is forecast to move eastward from eastern Ontario while a low pressure trough is forecast to strengthen west of the Great Lakes. Increasing cloudiness is forecast to spread eastward over southern Ontario, and winds are forecast to become east to southeasterly over all regions by late Wednesday.

During Thursday, a warm front is forecast to move northward over southern Ontario, causing cloudiness and scattered precipitation ahead of the front and southeasterly winds with increasing humidity following the front.

Air quality indices are forecast to be in the good to moderate categories in all forecast regions during Tuesday and Wednesday due to fine particles, ozone and nitrogen dioxide. Thursday's air quality indices are forecast to be in the good to moderate categories in southern Ontario and mostly in the good category elsewhere.

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.