Skip to main content
Français
Air Quality Ontario
AQHI
Alerts
Pollutants
Info
Data sets
AQHI
Alerts
Menu
Menu
AQHI
Alerts
Pollutants
Info
Data sets
Contact
Choose station
Barrie
Belleville
Brampton
Brantford
Burlington
Chatham
Cornwall
Dorset
Grand Bend
Guelph
Hamilton Downtown
Hamilton Mountain
Hamilton West
Kingston
Kitchener
London
Milton
Mississauga
Newmarket
North Bay
Oakville
Oshawa
Ottawa Downtown
Parry Sound
Peterborough
Port Stanley
Sarnia
Sault Ste. Marie
St. Catharines
Sudbury
Thunder Bay
Tiverton
Toronto Downtown
Toronto East
Toronto North
Toronto West
Windsor Downtown
Windsor West
Pollutants
Select pollutant
Ozone (O3)
Fine particulate matter (PM2.5)
Nitrogen dioxide (NO2)
Carbon monoxide (CO)
Sulphur dioxide (SO2)
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Month
January
February
March
April
May
June
July
August
September
October
November
December
Year
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
Chart
Table
St. Catharines: hourly ozone readings
From Nov-9-2025 EST to Nov-11-2025 EST.
Nov-9-2025 EST
Nov-10-2025 EST
Nov-11-2025 EST
Previous
Previous