During winters I would let my kids take a really long bath. Throw toys in there, play music, get some washable bath paint and let them go at it!
We also go to petsmart, our libraries have tons of activities outside of just reading story time, indoor play grounds, indoor kid museums, indoor pools, just walking around the mall is fun for her, friends houses, families houses
We have indoor slide and scooters, and a tent/fort and those keep them busy inside, most days. If it’s just cold out and the sun is also sort of out then we go to soft play/library as well, or just a walk
We stay at home a lot. The kids have lots of toys they can play with. We also do colouring, drawing, reading books, singing, making up games, pretend play, play doh, baking etc. It's OK to let them be bored and figure it out.
Do you have a pet store around you? We used to go walk around pet smart and look at all the animals. My toddler loved the fish !