**Problem** ``get_solarpostion`` method in ``modelchain.ModelChain.prepare_inputs`` does not use weather data. **To Reproduce** change line 745 - 746 ``` modelchain.py 755: self.solar_position = self.location.get_solarposition( 756: self.times, method=self.solar_position_method) ``` to ``` modelchain.py 755: self.solar_position = self.location.get_solarposition( 756: self.times, method=self.solar_position_method, 757: pressure=self.weather.pressure, 758: temperature=self.weather.temp_air) ``` **Versions:** - ``pvlib.__version__``: 0.5.2 - ``pandas.__version__``: 0.23.3 - python: 3.5.2