Air quality
Air quality in Ajax today
Updated
Good (US AQI 50) Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. Model estimate for Sun, Oct 25, 9:00 pm (01:00 UTC).
Live AQI, PM2.5, PM10 and ozone for Ajax, Ontario, Canada, with a 48-hour forecast and the best time to be outside.
- US AQI now
- 50 Good
- PM2.5
- 11 µg/m³ 0.8× WHO 24-h guideline
- PM10
- 11 µg/m³
- Ozone
- 49 µg/m³
- Dominant pollutant
- PM2.5 sub-index 50
- Best hour tomorrow
- 8:00 pm AQI 54
- European AQI
- 44
Air quality in Ajax right now
Right now the modelled US Air Quality Index for Ajax, Ontario, Canada is 50, which falls in the "Good" band (up to 50). Air quality is satisfactory and poses little or no risk; a good time for outdoor activity.
The index is driven mainly by PM2.5, whose own sub-index is 50. Fine and coarse particles come from traffic, heating, industry, dust and smoke; they build up on calm nights and clear when wind or rain arrives.
PM2.5 is 11 µg/m³, within the WHO 24-hour guideline of 15 µg/m³; PM10 is 11 µg/m³ against a guideline of 45; ozone is 49 µg/m³ (below the WHO 8-hour level of 100); nitrogen dioxide is 32 µg/m³ (above the 24-hour guideline of 25).
Also this hour: carbon monoxide 324 µg/m³.
NASA FIRMS shows 39 fire hotspots within 300 km in the last day (nearest about 62 km), but particle levels are not elevated enough to point to smoke right now.
Ajax AQI forecast: next 48 hours
Over the next 24 hours the AQI is forecast to range from 50 around Sun 9:00 pm to 59 around Mon 10:00 am, from "Good" at best to "Moderate" at worst.
The following day is expected to be cleaner, averaging about 33 against 55 for the next 24 hours.
| Local time (America/Toronto) | US AQI | Category | PM2.5 µg/m³ | PM10 µg/m³ | Ozone µg/m³ |
|---|---|---|---|---|---|
| Sun 9:00 pm | 50 | Good | 11.4 | 11 | 49 |
| Mon 12:00 am | 51 | Moderate | 15 | 15 | 42 |
| Mon 3:00 am | 53 | Moderate | 18.4 | 19 | 49 |
| Mon 6:00 am | 55 | Moderate | 20.8 | 21 | 52 |
| Mon 9:00 am | 58 | Moderate | 18.7 | 19 | 51 |
| Mon 12:00 pm | 59 | Moderate | 4 | 4 | 63 |
| Mon 3:00 pm | 57 | Moderate | 1.4 | 2 | 67 |
| Mon 6:00 pm | 56 | Moderate | 1.5 | 2 | 64 |
| Mon 9:00 pm | 54 | Moderate | 1.8 | 2 | 55 |
| Tue 12:00 am | 51 | Moderate | 1.4 | 2 | 51 |
| Tue 3:00 am | 43 | Good | 1.2 | 1 | 47 |
| Tue 6:00 am | 30 | Good | 1.2 | 1 | 44 |
| Tue 9:00 am | 21 | Good | 2.4 | 3 | 45 |
| Tue 12:00 pm | 22 | Good | 1.4 | 2 | 60 |
| Tue 3:00 pm | 25 | Good | 1.9 | 2 | 68 |
| Tue 6:00 pm | 29 | Good | 4.1 | 4 | 56 |
| Tue 9:00 pm | 27 | Good | 7.1 | 8 | 35 |
Every third hour of the CAMS forecast via Open-Meteo. US AQI uses rolling averages (24 h for particles, 8 h for ozone), so it moves more slowly than the hourly concentrations.
Best time to be outside in Ajax tomorrow
Between 6 am and 9 pm local time, the cleanest air tomorrow is forecast around 8:00 pm (AQI 54, Moderate) and the worst around 10:00 am (AQI 59). The difference across the day is small, so timing matters little.
Ajax vs the rest of Canada
Across 75 Canada cities we track, the average US AQI right now is 44 (Good). Ajax at 50 is 6 points worse than average.
For context, the median across 3,556 cities worldwide is 58.
Air quality in cities near Ajax
| City | Distance | US AQI | Category | PM2.5 µg/m³ |
|---|---|---|---|---|
| Whitby | 9 km | 45 | Good | 10.3 |
| Markham | 19 km | 51 | Moderate | 11.9 |
| Thornhill | 32 km | 41 | Good | 10.1 |
| Richmond Hill | 33 km | 41 | Good | 10.1 |
| Toronto | 33 km | 41 | Good | 10.1 |
| Vaughan | 37 km | 41 | Good | 10.1 |
| Aurora, ON | 39 km | 56 | Moderate | 12.2 |
| Etobicoke | 49 km | 41 | Good | 10.1 |
Model vs measured
We found no measured PM2.5 sensor cell within 25 km of Ajax, so the numbers on this page are model estimates. Models capture regional pollution well but can miss very local sources such as a busy road or a nearby fire.
Advice for sensitive groups
With the AQI at 50, there is no need for sensitive groups to change plans. People with asthma should still carry their reliever inhaler as usual.
What the US AQI numbers mean
| US AQI | Category | What it means |
|---|---|---|
| 0-50 | Good | Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. |
| 51-100 | Moderate | Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors. |
| 101-150 | Unhealthy for Sensitive Groups | People with heart or lung disease, older adults, children and teens should cut back on prolonged or heavy exertion outdoors. |
| 151-200 | Unhealthy | Everyone should reduce prolonged or heavy exertion outdoors; sensitive groups should avoid it and keep windows closed. |
| 201-300 | Very Unhealthy | Health alert: everyone should avoid prolonged or heavy exertion outdoors, and sensitive groups should stay indoors. |
| 301-500 | Hazardous | Emergency conditions: everyone should avoid all outdoor physical activity and stay indoors with filtered air if possible. The scale tops out at 500; heavier dust or smoke is shown as 500. |
Values on this page are modelled by CAMS (Copernicus) and served by Open-Meteo; they are estimates for the area around the city centre, not readings from an official monitor.
Nearby cities
More for Ajax
Air quality elsewhere
Data: Open-Meteo Air Quality API, Copernicus Atmosphere Monitoring Service (CAMS), NASA FIRMS.