DHT22 sensor warm-up time

Allow stabilization after power-on before trusting humidity readings for condensation or mold decisions.

Aosong AM2302 DHT22 temperature and humidity sensor module on a black breakout board
The DHT22 (AM2302) is the digital humidity–temperature sensor used in many DIY space builds. Photo: Suyash Dwivedi. CC BY-SA 4.0

DHT22 humidity sensors equilibrate with surrounding air after power application. Temperature responds faster; humidity may drift toward true values over several minutes, especially if the sensor was stored in a cold truck before install. Firmware and installers should ignore or flag early samples so JSON and LCD do not alarm on transient RH.

Timeline graph showing humidity settling after power-on versus faster temperature response
Humidity readings stabilize over minutes after cold storage or rapid temperature change.

Boot behavior

Skip publishing humidity for the first **one to three minutes** after reset, or mark reads as warming in serial logs via serial debug. Align with main loop timer so HTTP still serves temperature if needed.

Environmental triggers

  • Cold snap after warm storage: humidity lags real air.
  • Door event mixing humid outdoor air: wait one poll cycle before alerts.
  • Vehicle heat nearby: see stored vehicle heat.

User-facing impact

Dashboard history inherits warm-up blips if inserts run immediately: pair with retry policy and condensation basics for interpretation, not panic.