Get your umbrellas and go for a walk. Talk about how the rain is good for plants and makes them grow taller.
Jump into puddles. Find out what mud feels like between bare toes. Let your toddler frolic around and get wet before you head indoors. What does rain feel like and sound like? This is a great time to teach vocabulary words, wet, rain, mud, sky, puddle; repeat the words again and again to toddler, and let him or her try to repeat them.