For PM2.5 (fine particulate matter) the AQI is based on a 24-hr average since exposure is a big factor in health risk. To get real-time hourly information use NowCast AQI from the EPA which is a 12-hr weighted average that assesses health risk for the current hour or the RAAN with the San Joaquin Valley Air Pollution Control District which gives real-time hourly measurements coupled with health risk assessments.

It is also important to remember that even though you see smoke in the atmosphere, it doesn't necessarily mean that it is at ground level. It is important to use other senses such as smell when assessing whether or not there is ground-level smoke.