In case when the thermometer and barometer readings are not accurate, this is how you can re-calibrate it. Go to Barometer and temperature mode. Hold Adjust button until the current temperature value start to flash. To switch the adjust mode between temperature and pressure readings, press the Mode button. Use the Light ( decrease ) and Alti ( increase ) button to adjust the temperature or pressure value. Press Adjust button to apply the new values. Note: to reset the calibrated values back to factory values, just simply press the Light and Alti buttons simultaneously. You should see the OFF message. References or Credits: http://ftp.casio.co.jp/pub/world_manual/wat/en/qw3202.pdf