| Station | Location | O3 |
|---|---|---|
| Barrie | 83 Perry St. | 18 |
| Belleville | 2 Sidney St., Water Treatment Plant | 15 |
| Brampton | 109 Mclaughlin Rd. S. | 23 |
| Brantford | 324 Grand River Ave. | 24 |
| Burlington | North Shore Blvd. E. Lakeshore Rd. | 20 |
| Chatham | 435 Grand Ave. W. | 26 |
| Cornwall | Bedford St. 3rd St. W. | 16 |
| Dorset | 1026 Bellwood Acres Rd. | 18 |
| Grand Bend | Point Blake Conservation Area | 30 |
| Guelph | Exhibition St. Clark St. W. | 25 |
| Hamilton Downtown | Elgin St. Kelly St. | 19 |
| Hamilton Mountain | 250 Fennell Ave. W. | 21 |
| Hamilton West | Main St. W. Hwy 403 | 21 |
| Kingston | 23 Beechgrove Lane | 13 |
| Kitchener | West Ave. Homewood Ave. | 19 |
| London | 42 St. Julien St. | 22 |
| Milton | 1120 Main St. E. | 21 |
| Mississauga | 3359 Mississauga Rd. N., U of T Campus | 18 |
| Newmarket | Eagle St. W. McCaffrey Rd. | 19 |
| North Bay | Elgin St. Kelly St. | 21 |
| Oakville | Eighth Line, Glenashton Dr., Halton Res. | 22 |
| Oshawa | Brittania Ave. W., Ep Taylor Stables | 16 |
| Ottawa Downtown | Rideau St. Wurtemburg St. | 17 |
| Parry Sound | 7 Bay St. | 19 |
| Peterborough | 10 Hospital Dr. | 14 |
| Port Stanley | 43665 Dexter Line, Elgin Water T. Plt | 19 |
| Sarnia | 700 Christina St. N. | 24 |
| Sault Ste. Marie | Sault College | 27 |
| St. Catharines | Argyle Cres., Pump Stn. | 19 |
| Sudbury | 155 Elm St. | 21 |
| Thunder Bay | 421 James St. S. | 8 |
| Tiverton | 4th Concession, Bruce Rd. 23 | 30 |
| Toronto Downtown | 55 John St. | 12 |
| Toronto East | Kennedy Rd. Lawrence Ave. E. | 14 |
| Toronto North | 4905 Dufferin St., Eccc | 16 |
| Toronto West | 125 Resources Rd. | 12 |
| Windsor Downtown | 467 University Ave. W. | 14 |
| Windsor West | College Ave. South St. | 19 |
ozone O3 Concentrations for Friday, October 31, 2025, 5:00 am
Note: The pollutant concentrations on this web page are based on automatically polled data and have not undergone final verification.
Note: N/A (not available) denotes invalid or missing data.
Ontario 1-hour AAQC for O3 = 80 ppb
