1-Stone Art : Gather up flat stones from the backyard, then decorate them with washable poster paint(water color paints wont show on the stones).You can also use glue on shells, leaves and other outdoor objects to create faces or any design your child chooses.
2-Waterworks : Provide a bucket of water and a big brush and let your child "paint" a design on the house or sidewalk. Then watch him learn a simple science lesson as his pictures evaporate in the sunlight.
3- Shadow People : using chalk,trace eachothers shadows on the pavement. Wait on hour and trace them again, ask your preschooler; what's the same?ahead different?check again at the end of the day.Will a child's shadow ever be longer than her parents? VARIATION: trace each others shadows on paper, then paint and display them.