You're not the only one.  But we have enough activities that take us from home that it helps.  We have HS co-op, indoor track, inside field trips, and more.

You might try leaving the house one morning or afternoon (dreary days are best!) and going to the public library and working.  The change of place can be good.

You might also save some "fun" activities for wintertime.  Get a Mary Ann Kohl art book and do some fun hands-on stuff.

Get involved with community service, especially during the holidays.  Soon it will be time for Samaritan's Purse to send out boxes.  Spending a day at one of their distribution sites would do every some good. 

Visit a nursing home; do some Christmas caroling; bake a lot to give to neighbors & friends...or to fill your freezer for sping & summer when you don't want to heat up the kitchen; volunteer at Project Read adult literacy; ...any volunteer time - as a family, or something separate for everyone.

Just some ideas off the top of my head!  We HS in our walk-out basement and we made sure to put our desks by the 8-foot sliding door and the window so we wouldn't feel trapped.  We have lots of wildlife around...so we usually get distracted, but it keeps us glad we're inside & warm!

Hi, Our issue is more with general boredom and tedium maybe some of these ideas will help.

Take a break from normal homeschool lessons before Christmas (or your winter holiday) and focus on doing fun things for that. Cooking, crafts, model train exhbits, etc. Take a week off after Christmas to relax and play around with new stuff received.

In dead of winter totally change up the homeschool lessons you do. Add in new things that are completely different and pare back the basics. Don't have the lessons be the same as spring and fall or by late winter or early spring everyone may be sick of the same old stuff being done daily or even 3x a week.  For example add in poetry if you've not done that, do art lessons, do whatever you didn't do in the fall due to feeling too busy.

Do hands on stuff like science experiments, craft kits and fun kits that are supposedly "educational" even if they seem like fluff.

Consider a once weekly museum or historical site trip out of the house, weather permitting.

Invite friends over for more playdates than usual. Go to their houses to get out.

Add in a short session of an outside class that perhaps you'd not planned on doing. Year before last mine did a last minute 6 week pottery class & it broke the tedium.

Get outside even in the freezing weather & play or do nature hikes. After that they may be happy to sit down and do calm activities & may be tired out.

Do a read aloud of a book then see the movie & discuss how they were different.

Watch documentaries on TV that are exciting & interesting & count that as 'school work'.

Start a new topic of study that is short term. Let your kids pick the topic of their choice. Be flexible & don't mandate that it fit with your year's plans.

Spend more time exploring local libraries. Let your kids really look around to see what they have and let them borrow books.

Buy or borrow new board games and learn to play them. Find some new family favorites. Two of our recent favorites are Settlers of Catan with Cities & Knights add on & Ticket to Ride.

HTH!

You are certainly not the only one that struggles with this.

This year we are purchasing one of those jogging trampolines for inside.  Hopefully that will help get some energy out.

I also would like to learn a new hobby myself and encourage children to do the same.

I will continue to monitor this thread for other ideas.  Thanks for posting.

I have stocked our home with board games (some I'd never heard of before) and science experiment kids and craft kits from tag sales & charity thrift shops. For 50 cents to $1 mostly. Some of those educational kits are fluff IMO but fun to tinker with especially to alleviate boredom. Plus if they are not so great having spent $1 instead of the retail $15 or $20 is not too painful. Sometimes the kits are great but just have one thing done/missing, like a big set of crystal growing experiments from Smithsonian we got for $1 had one thing done out of the 12-15 in the box. What a steal. I keep the kits in my unfinished basement & send the kids down to pick something out when they are bored. "Go find a kit to work on." They like having freedom to pick.

We are an arts and crafts family and can burn a half or whole day doing that stuff. I recall one winter day we stayed in PJs & worked on polymer clay all day (the kids first time working with it). I am a "process not product" attitude person. The boys loved working with the pasta machine with the clay and making the colors smear with each time through it.

Another thing my boys love is cooking and baking. A big hit with them is the cookbook series (check your library, I got mine on PBS)----Top Secret Recipes. This series imitates restaurant food or store bought food like homemade Oreos and such. The boys think it is great fun to imitate those foods & see which is better. So far they have preferred the homemade versions & are realizing higher quality in from scratch cooking even though they loved the store-bought originals or restaurant versions! The potato skins took over 3 hours to make, lots of work that keeps them busy. If you make your kids help clean up that keeps them busy too then they are happy to be let go to play.

I find my kids bicker or complain about homeschooling when they are too bored. So in the winter fending off boredom and not letting it get to the bickering stage is a goal of mine.

I will keep reading what others post as I always need ideas too!