[Barrow4491]

... It should not matter for the AQI.

I think it matters. Temperature affects how internally the sensor calculates RH.
And RH is used to compensate PM readings.

PM readings should be compensated in function of RH, Sharp even sugests this function:

beta = Humidity factor
if (rh > 50.0) beta = 1- 0.01467 * (rh - 50.0);


WeatherDuino AQM usis this:
if (Humidity > 50.0) beta = 1.0 - (0.016 * (Humidity - 50.0));
PM2.5 = PM2.5_raw * beta


However, as the enclosure designed by Barrow4491 allows a great air flow, the heat produced by the Nano and regulator shouldn't affect greatly the readings.

By the way:
Barrow4491, you did a nice work.

Thanks
When I was designing the screen I wanted the centrepanel vertical with the sensors on one side so that both got a good clear airflow and the pcb on the other side with the HTU21D at the bottom to avoid any heat effect from the regulator or Nano.
Regards
Jim