He often plays upstairs, so just by saying let's play downstairs, it sometimes gets him excited to play with different toys.
Put Toys Out of Reach
Certain toys I put away and only get out when he needs a suggestion for an activity. I do this with puzzles, games and his Melissa & Doug fishing set. Then, he doesn't lose all of the pieces amongst his other toys and he's excited to play with it when I do get them out.
I like to get Parker's paint set out or a colouring book when he's bored. To be honest it's not a long activity usually, but it gives him something different to do. And because it's not something he does a lot he really enjoys it. As he gets older we will likely start doing more specific creative activities and crafts!
I love getting out the paint set or some other learning activity for him to occupy his time. Education.com is a great website to find a variety of worksheets that will keep your kids occupied while they are learning something! They have so many worksheets, games, colouring pages. I find that if I give Parker something productive to do he is entertained and so much happier. I think some of their items might be too tricky for Parker yet, but there were also a ton of preschool worksheets that could get him started with tracing shapes, colouring and writing letters.
Do you have any other ideas for fun ways to keep kids occupied when it's cold outside?