PMS7003, and most probably all other low-cost PM sensors with the same working principle, is not made to be used outdoors. Although used in many DIY projects for outdoor air quality monitoring, researches show that high humidity badly affects the PM measurements. Some have tried to heat the air before entering the sensor or to derive a correction factor, but mostly unsuccessfully.

These sensors are not as accurate as more expensive professional devices but are good enough to give an idea of the pollution in the air.

From my experience so far, PMS7003 measurements are comparable to official government air quality measurements available for my neighborhood.