Use the side of a building or the ground to experiment with shadows. Ask children to see if they can make animal shapes out of their own shadows by twisting their bodies or forming their hands. Hang up a white sheet from a rope or have two adults hold it up. Have one child stand behind the sheet and try to form a shape. The other children must guess what his shadow is supposed to be.
Have children conduct a heat experiment while also playing a game with ice. Give each child a few ice cubes. Start a stopwatch, then challenge children to see how quickly they can melt their ice. Don't give any guidelines or suggestions so children can use their creativity. The sun will quickly melt the cubes if children place them on the ground, but children can speed up the process by breaking the cubes apart or using the heat of their hands as well. Compare the times for each child and ask the fastest children to share their techniques with the class.
Add some excitement to a game of tic-tac-toe or hopscotch by making the boards out of disappearing water. Bring spray bottles filled with water outside. Take children to a paved surface such as a sidewalk or empty parking lot. Use the bottle to spray the shape of a tic-tac-toe board onto the ground. Give two children their own spray bottles so they can spray x and o shapes onto spaces. They must finish the game before the sun dries the water. Create hopscotch boards, then see how many times children can complete the game before the board disappears.
Most children enjoy getting wet and messy, but it can be miserable for you to have a group of wet children. They'll dry off quickly on a sunny day, so head outside with a bucket full of water balloons. Pair children up and have each child stand across from her partner. Give one child in each pair a water balloon and have her toss it gently to her partner. He must catch it and toss it back to her. If they toss the balloon without it breaking, have them take a step away from each other and toss it again.