The HTU21D is a cheap, user-friendly, accurate, digital humidity and temperature sensor.
This sensor is ideal for sensing an open/enclosed environment, data logging is also simplified, and perfect for weather stations or humidor control systems.
Requirement is only two lines for I2C communication and you'll have relative humidity readings and very accurate temperature readings as a bonus! Only four pins are needed to be hooked up in order to start using this sensor in a project. One for VCC, one for GND, and two data lines for I2C communication.
This breakout board has built in 4.7k pull up resistors for I2C communications.
Note: Full drops of water can damage the sensor. We recommend wrapping the board in Teflon/irrigation tape for extreme conditions where water droplets may find their way onto the sensor.