Simple way to create rain. Lets make some selection with "magic wand", start from sky. Keep your wand tolerance around 20 and antialiasing on, click somewhere in sky to add more sky to your selection push "Shift Button" down (in keyboard) keep pressing shift, (You should see a small Plus icon instead cf magic wand icon... meaning that you can add to selection) click in sky area that is not selected yet....You notice selection area grows. If you need to remove some area from selection so simply "Alt Click" to move part of area. Before we save the selection we add some more selection to sky but now use "Lasso" tool. Select Lasso tool and make "Feather" propeties at least 5. Now Shift or Alt clicking add or remove parts from horizon. Selection should be smooth between sky and horizon. When you are done with selection its time to save it choose "Select Menu > Save Selection" Name your selection Sky. Now invert your selection ("Select Menu > Inverse") and save selection again name it Middle. Using Lasso remove (Alt clicking) stuff that is far away in picture like horizon, houses, wood etc. In this image I kept ,cars ,ground ,walkway and pillar on the right. Save Your selection and name it Ground. Create 5 new layers name them Sky, Middle, Ground, Rain and Darkenig.(Darkening in bottom layer over background). Maybe your image need some darkening. Select the Darkenig layer and fill it using gradient tool (black and white). Draw from top right to down in 75 decrees angle. In your layer opion box (F7) select Multiply and make Opacity around 30 (or Draw slider for live result). You see sky became darker.(try some other layer options as well maybe Color and Overlay). Dont make it too dark since you are going to use more layers whitch add some darkening. Fill your Rain layer with white color "Edit > Fill". Draw some black strokes/lines using painbrush tool texture comb or similar (draw diagonal around 75 degrees). Blur Your Rain layer with "Motion Blur" using angle 75 distance maybe around 400. Adjust color to make it more gray "Image > Adjust > Variations..." Make it more lighter it should be gray color. Make Rain layer properties Multiply and make Opacity around 30. (This is your rain template). Now - lets add some fake rain. Select your Rain layer ,select all, "Ctrl+A" copy, "Ctrl+C" and paste, "Ctrl+V" now you have a new layer over Rain layer, use properties Overlay opacity 40. Lets add some effects in "Filter > Noise > Add Noise".Select Uniform Monochrome and Amount 45. In "Filter > Blur > Motion Blur" angle 75 pixel amount 11. And Its rainy day.... Lets select rain layer (rain template) again now we add some selection, "Select Menu > Load Selection". channel sky selection. Now "Ctrl+C" copy. Activate Sky layer and paste, "Ctrl+V". Options in layer >>Multiply and Opacity low around 12. Go to "Filter > Noise > Add Noise".Select Gaussian Monochrome and Amount around 20. (Fine rain far away) In "Filter > Blur > Motion Blur" angle 75 pixel amount around 11. Now its a time to make some foreground rain a bit heavier. Select Rain layer then "Select Menu > Load Selection" Channel Middle. "Ctrl+C" copy selection load Middle layer "Ctrl+v" Paste. Change layer properties to HARD LIGHT opacity 20. Add some heavy noise and blur BUT change the angle to lets say 85 tweak little with pixel distanse as well. To make your street more wet use your ground selection... copy from rain layer as before etc. Use diffrent blur angle -75 smaller noise. In layer optionsa Color burn gives a nice dark street, Screen gives light street.. tweak yorself.