The RHT03 (also known by DHT-22) is a low cost humidity and temperature sensor with a single wire digital interface.
The sensor is calibrated and doesn't require extra components so you can get right to measuring relative humidity and temperature.

Features:

• 3.3-6V Input
• 1-1.5mA measuring current
• 40-50 uA standby current
• Humidity from 0-100% RH
• -40 - 80 degrees C temperature range
• +-2% RH accuracy
• +-0.5 degrees C

Documents:

• Datasheet
• Example Code
• GitHub