Create mud by mixing sand, dirt and water in a large bucket. Take the preschoolers outside and allow them to help make the mud by adding sand and mud to the bucket, slowly adding in water and then stirring until the mixture has a very thick consistency. Provide a pie tin and let preschoolers get messy making mud pies. Provide decorations like grass, flower petals and leaves. Allow the pies to bake in the sun.
Painting can be an exciting but untidy activity for preschoolers. Do this activity outdoors, where cleanup is easier. Create paint by mixing equal parts cornstarch and water and then adding food coloring. Children can help mix the paint in shallow containers. Encourage children to paint on the fence, the sidewalk and even on themselves with brushes, sponges or their fingers. The paint washes off quite easily with water.
Provide a wide range of messy activities for toddlers using a kiddie pool. Children will enjoy being out in the summer sun while getting dirty and learning about concepts such as volume and measurement. Blow up a kiddie pool and use it as a container for sensory materials such as puffed rice, whipped cream, bird seed and sand. Provide things that children can use to scoop the materials, such as spoons, shovels and measuring cups, along with containers to hold the scooped materials. Children can wear bathing suits and get into the kiddie pool for a complete sensory experience.
Preschoolers enjoy spray-painting. It is an activity sure to make a mess, and is therefore best done outdoors on the grass. Fill spray bottles with water and food coloring or paint that has been watered down. Provide children with stencils in a variety of shapes. Show them how to squeeze the spray bottle. Children can tape the stencils onto paper on an art easel and then use the bottles to splatter paint all over the paper. The preschoolers can remove the stencil to reveal the design.