Original photo of my friend Guilherme.
Picture taken in Chicago of a beautiful warm day.
Merged both pictures to replace the grey sky in the background. The process is to open both picture as layers in Photoshop. Then use the blending mode that better serve you for best to fix the picture. A mask will be needed to erase places where the clouds are not needed. After merge both layers, and "Voila" this is the final result.
