What's a heat index???

I have never known heat until living in NC! Who would have thought since we just moved from Arizona! The news today said the "heat index" (whatever that is) will be around 110 degrees today and will hold steady through the week. In my world, that means I've got to find lots of interesting indoor activities to keep a 14 month old happy. It's even too hot to play in the pool out back. When C. starts to turn a sugar beet color, it's time to go indoors. I just don't think we are built for this heat! Last weekend, R. and I worked in our front yard trimming bushes and weeding flower beds (pretending to know what we're doing!) all the while, dripping with sweat like we have finished the Boston Marathon! Our neighbors across the street were also doing yardwork and hardly broke a sweat! I hope it's possible to climatize to the weather, I don't want to be known as the "new sweaty girl" in the neighborhood!

Does anyone have any suggestions for indoor activities during this heat??