How to find the nearest location which has sunny forecast

Karlson is correct. The next best thing to do is look at historical data, if you have copious amounts of free time, to see locations weather history around you.

http://www.ncdc.noaa.gov/

You can do this with a predictive weather map. For example, http://www.weather-forecast.com lets you get a map centred around any country or (for some countries) a state/province, fast forward to a date (up to 10 days), then look for sun.

For example, here's their map centred around Washington State for next Saturday as an example. Each of those icons gives you a basic local forecast when mouseovered:

How reliable is it? Depends on the local weather data, but it's the simplest way I've found to browse for nearby sunshine.

The website's navigation is a bit... old-school. Start at http://www.weather-forecast.com/maps then find a country of interest, then hit the + button to choose a state/province then press the ? arrow or drag the slider to navigate to the date and time you want.

Of course, how useful the information shown on the map is will vary by region...

You can use Where2go from Meteoblue, they have very accurate forecast predictions as well https://www.meteoblue.com/en/weather/outdoorsports/where2go