At the heart of the module is the next-generation digital temperature, humidity and pressure sensor manufactured by Bosch – BME280. It’s a successor to sensors like BMP180, BMP085 or BMP183.
This precision sensor can measure relative humidity from 0 to 100% with ±3% accuracy, barometric pressure from 300Pa to 1100 hPa with ±1 hPa absolute accuracy, and temperature from -40°C to 85°C with ±1.0°C accuracy.
The pressure measurements are so precise (low altitude noise of 0.25m), you can even use it as an altimeter with ±1 meter accuracy.