Things you need: hot items and cold items. I used gel-filled ice packs (they stay squishy when frozen) and rice-filled heat bags. Use the ice packs straight from the freezer and warm the heat bags in the microwave. Be careful not to get the heat bags too hot!
What to do: Place your hot and cold items on the floor and let your little one explore. It's as simple as that! I've done this activity before with Olive, but the first time we did it, I just let her feel around for about 5 minutes. After she had done some sensory exploring, I started talking with her. "Oh, this is cold! Is that one warm? Ooohh, that feels nice and cozy! Should we put the cold one on our feet? Oh boy, it's freezing!" and so on.
Like with any sensory activity, try not to push them. It's really all about exploring. If they seem like they need help, you can guide them, but try to leave them to discover things on their own. Even from the first time we did this, Olive chose - on her own - to step on the items and lay on them.
Feeling the cold
Feeling the hot/warm
Laying on the hot/warm
Laying on the cold
Everything still goes in the mouth! Ay yai yai!