That is the truth. Many people dread a rainy day but you need to push that emotion aside and embrace the rain and even run outside and splash in the puddles. After all, it is only water and will not dissolve you like the wicked witch in "The Wizard of Oz."
Pull out some old clothes for your kids to dress up in. Have a fun parade using as many silly costumes as you can. You can document these antics on film and show them to daddy when he comes home. You can take photos of your rainy day and then make a scrapbook of the fun you creative - now stored as a permanent memory. Another great idea is to lay some "rainy day" items out on the floor: umbrella, boots, raincoat etc. and then take some flashcards and label them. Use the cards as a teaching tool for language/vocabulary building.
Here is a book you might pick up to read and enjoy together on another rainy day.