Sometimes the weather just won't give you the perfect shot you're hanging around for. Luckily, editing packages can sometimes rescue the situation. For this tip you need a few sky shots, so it's worth starting a sky library next time you see a beautiful vista and have your camera handy.
Use the lasso tool to select the non-sky area of your gloomy photo, then copy (Ctrl, C) and paste (Ctrl, V) this on to a 'nice weather' sky shot - it will form a new layer. Move your cut-out landscape to the top in the layers palette, then adjust the positioning. Use the Blur tool at the horizon to add depth.