The DHT20 is a nice but inexpensive temperature and humidity sensor from the same folks that brought us the DHT22.
unlike classic DHT sensors, it has an I2C interface! That’s right, you do not need to use a bit-bang timing-specific protocol to talk to the DHT20, it uses plain-old-I2C. And, you can power it with anything from 2.5V to 5.5V so it’s good with 3V or 5V microcontrollers.
This sensor has a typical accuracy of ±2% relative humidity, and ±0.3 °C at 20-80% RH and 20-60 °C.

Specifications:

I2C address 0x38 (cannot be changed)
2.5V to 5.5V power and logic level
Pin order from Left to Right: Power, SDA, Ground, SCL
Built in 4.7K I2C pull-up resistors.
Usage Humidity: 0… 100%RH
Usage Temperature: -40oC – 80oC
Typical accuracy of ±2% relative humidity, and ±0.3 °C at 20-80% RH and 20-60 °C
Overall accuracy of ±3% relative humidity, and ±0.5 °C