Read books and poems about clouds or weather with your preschoolers. Some books about clouds include "Cloudy with a Chance of Meatballs" and "It Looks Like Spilt Milk". Talk with children about types of clouds that they see and what the books say about clouds. Draw cloud pictures and have children dictate a sentence about shapes that they see in their cloud pictures.
Briefly discuss the different types of clouds and what they look like. Explain to children that rain and snow come from certain types of clouds. Make a homemade cloud by boiling water in a teakettle and looking at the steam that rises from the boiling water. Hold an aluminum roasting pan or pie pan over the steam and watch the water condense and drip off of the pan like rain. Explain that this is similar to the way that water evaporates and condenses into rain.
You can do many different cloud art projects with cotton balls. Stretch and pull the cotton balls before gluing them down to make different types of clouds. Help children label the types of clouds and talk about which ones mean good weather and which mean rain or snow. Mix shaving foam with a bit of white glue and have children spread it onto paper and allow it to dry to make puffy clouds. Blot white paint into the middle of a blue piece of paper, fold it in half and rub the sides together. Unfold the paper and have children talk about the shapes they see in their pictures.
Your imagination is the limit when it comes to other cloud-themed activities. Serve marshmallows for snacks and talk about how marshmallows are similar to and different from clouds. Make a variety of cloud shapes and have children match up the ones that are similar. Sing the song "Cloudy" to the tune of "Bingo (Was His Name-O)." Glue cotton balls to paper clouds to make cloud puppets and have children use them when you sing cloud songs or read a cloud-related book.