For the measurement of temperature, humidity, rain, wind and air pressure I decided for outdoor sensors of EVL. They work in the 868Mhz band and can be easily read using a receiver.
At the time of my planning, a binding for openHAB was developed.
The following components were used..
Additionally, To measure the air pressure i use a self-development sensor on the basis of a Jeenodes. This is a low power Arduino clone which already has a 868MHz radio module and could be easily integrated into the existing infrastructure.