Even though the sun is here, clouds and rain roll in from time to time. This is how you can create your own weather.
Start with creating a circle, fill it with blue.
Use OPTION click + DRAG to create duplicates of the circle half way over each of the existing circle. The center of the new circle should be on the right edge of the previous circle and your Smart Guides will let you know when you make contact with the circle center on the edge of the previous circle
Do this for a second row as well, shifting the top set so that is is halfway in line with the first set of circles.
Select all the circles, the use the Pathfinder Panel to Unite them all together into one unit.
Draw a straight line under the clouds.
Round the ends of the line with the round cap end in the Stroke panel.
OPTION + CLICK & DRAG the line, then use COMMAND + D to duplicate the line several times.
Using the Direct Selection Tool to select the bottom point of the first line, then use SHIFT + UP Arrow to move the line end up. Do this to the bottom point of each line, up and down to create a stagger effect. SHIFT + UP (or down) ARROW moves the line up or down 10 units, keeping the line lengths in a common distance.
Select all the lines of rain, then select the Shear Tool and OPTION + CLICK on the upper left corner of the group of rain lines. This sets the shear point AND open he Shear dialog box.
Then set the shear angle and click OK.
There is the final rain.
You can also take the bottom side of the clouds off to make a flat cloud.