The inland setting means local environmental conditions are shaped more by urban density than coastal influences.
In line with average conditions across San Francisco
24-Hour AQI Trend
Pollutant Breakdown
Peer Comparison
In line with average conditions across San Francisco
Why Union Square, San Francisco's Air Is What It Is
Union Square, San Francisco sits in an inland urban setting where local environmental conditions are shaped primarily by density and development patterns. Temperature swings between day and night can be more pronounced than in coastal areas.
Historical Context
Current AQI of 31 reflects recent monitoring data. Local conditions can shift with weather patterns, traffic volume, and seasonal factors.
24-Hour Hourly Forecast
Best window: 05:00 (AQI 31) · Peak AQI: 41 at 21:00
| Time | AQI | Temp (°F) | Humidity | Wind (mph) | PM2.5 | PM10 |
|---|---|---|---|---|---|---|
| 00:00 | 36 | 129.6 | 67% | 5.3 | 9.5 | 14.8 |
| 01:00 | 35 | 128.5 | 68% | 1.8 | 8.8 | 13.5 |
| 02:00 | 34 | 128.5 | 64% | 2.7 | 8.1 | 12.5 |
| 03:00 | 33 | 126.9 | 63% | 2.9 | 7.8 | 11.9 |
| 04:00 | 32 | 124.7 | 67% | 4.3 | 7.8 | 12.0 |
| 05:00 | 31 | 122.5 | 74% | 3.2 | 7.1 | 10.9 |
| 06:00 | 31 | 123.3 | 70% | 2.1 | 6.8 | 10.2 |
| 07:00 | 31 | 125.6 | 74% | 0.7 | 6.3 | 9.5 |
| 08:00 | 31 | 133.3 | 76% | 0.9 | 6.1 | 9.4 |
| 09:00 | 31 | 137.1 | 65% | 0.6 | 6.2 | 9.5 |
| 10:00 | 31 | 142.5 | 57% | 2.5 | 6.7 | 10.2 |
| 11:00 | 31 | 149.2 | 47% | 4.5 | 6.7 | 10.1 |
| 12:00 | 32 | 151.9 | 46% | 6.5 | 6.6 | 10.1 |
| 13:00 | 32 | 156.7 | 43% | 6.4 | 6.7 | 10.3 |
| 14:00 | 33 | 158.0 | 42% | 7.5 | 6.7 | 10.4 |
| 15:00 | 34 | 160.0 | 40% | 7.0 | 6.5 | 10.0 |
| 16:00 | 36 | 160.7 | 37% | 6.8 | 5.8 | 8.9 |
| 17:00 | 37 | 165.0 | 18% | 9.2 | 5.1 | 7.7 |
| 18:00 | 38 | 163.9 | 19% | 11.1 | 5.7 | 8.6 |
| 19:00 | 39 | 158.4 | 23% | 10.2 | 6.0 | 8.8 |
| 20:00 | 40 | 153.9 | 24% | 9.6 | 6.5 | 9.7 |
| 21:00 | 41 | 150.1 | 26% | 10.3 | 5.9 | 8.6 |
| 22:00 | 41 | 146.7 | 28% | 9.4 | 5.5 | 7.8 |
| 23:00 | 41 | 144.5 | 30% | 10.4 | 5.1 | 7.1 |
Air quality is forecast to be good for most of the day. Great time for outdoor activities!
Planning your day in Union Square, San Francisco? The hourly forecast shows the best air quality during 05:00 (AQI 31) with a low of 31 at 05:00. The most challenging conditions occur around 21:00 (AQI 41) when AQI peaks at 41 at 21:00. According to standard health guidance, the forecast for Union Square, San Francisco can help with planning but should be used alongside current readings. Air quality is forecast to be good for most of the day. Great time for outdoor activities! Conditions in specific parts of 94104 may differ from the overall forecast.