What is the best way for measuring the temperature for a weatherstation. The temperature would be between about -30°C to 30°C and I would like to have a accuracy of about 0.1°C to 0.5°C. I was thinking about using some Temperature Resistors in parallel but I think I won't get the high accuracy for this. With another temperature sensor like the lm75 there is a too high inaccuracy.
Resistance temperature detector (RTD)
Historically, this has been the preferred solution for temperature sensing with the kinds of accuracy you desire.
If you want to build an RTD signal conditioning circuit out of OpAmps, this application note might help. There are also ADCs with integrated front ends for RTD.
Over the last two decades, the thermistor materials have improved, and we have thermistors which can achieve ±0.1°C accuracy.
This thermistor, for example.