Photographing night and day sky means continuous monitoring of local weather and space weather. There is a number of meteorological sites: Finnish Meteorological Institute (FMI) gives a comprehensive look at weather and updates forecast several times a day. They also have some nice satellite images of clouds, although their update rate is not always good. Foreca also gives detailed forecasts. Both FMI and Foreca have a lot of other data: local forecasts, radar data of rain plus rain forecast as well as latest weather observations. For real-time weather data and weather graphs in Turku check Åbo Akademi's weather station.
A new site for real time lightning observations is provided by FLC. European storm forecast is provided by ESTOFEX.
A most wonderful site with a multitude of forecasts is given by Polish Numerical Weather forecast ICM. In this site you choose "Meteorograms" and click your location on a map and get a 3 days' meteorogram with a lot of data. Data is updated every twelve hours and a new set of data is available at about 02UT and 14UT. Choosing "Detailed Maps" you have access to a large set of thumbnail maps of different weather data. Click one of the thumbnails and get an enlarged picture, in which you can scroll forwards and backwards in 3 hours' steps.
Like Polish meteograms above nice data is provided also by Meteoblue. Give your site and click "Air" to get a local meteorogram. Note: there is a lot of other data and a link to an experimental astronomical seeing prediction - click "Sky"!
A low resolution satellite image (updated hourly) is given by Austrian ZAMG. An animated cloud sequence is also provided ZAMG.
You can check current and coming weather in North-America or in Canada. Sure enough, there must be even better places for North-Americans, but from European vantage point these are much of what is needed.
Photographing weather and weather related phenomena is a hobby opening our eyes to the beauty of our blue planet but also it makes us to appreciate the forces that govern our everyday life. Abby from Delaware pointed us a great site to learn more about weather photography.