I started with the APIXU driver. Have a look here: Apixu.com worldwide weather data with outside lux. No PWS or server setup
That will give you a lot of values to play around with. Not always 100% accurate, but a good start.
You can always install your own weather station later...
You can then fine tune your rules to turn on the lamp if sunset -60 and cloudy, or illuminance < number, etc.
