Museums are great places to while away a few hours, especially in winter. They're a great way to learn about local heritage or just get a feel for the place you're in.
When I'm on holiday I love to find out about the place where I'm staying - what makes it tick, how it came to be what it is; and often there'll be a particular street or building that grabs my attention and makes me want to know more. If the town has a museum, I'm in there like a shot.
Sussex has a variety of museums that reflect its heritage as well as its focus on the future. For a family day out, a great place to start is the Weald & Downland Open Air Museum at Singleton, where you can learn how agriculture and the landscape shape what we see today. It's a large-scale experience, indoor and outdoor, with plenty of room to roam, so if Mum wants to marvel at wonderful architecture, Dad wants to go for a walk and the kids are enthralled by practical demonstrations, it's all there. Similarly, the Amberley Museum & Heritage Centre has rides, demonstrations and plenty of space, or there's the Bentley Wildfowl and Motor Museum (an odd combination on paper, but it does work!).
For indoor museums with quirky appeal, Horsham is pretty hard to beat. Its eclectic collection is like a treasure trove and really well curated. Not far away, Dorking Museum is another little gem.
Tangmere is home to a well-known Military & Aviation Museum, and if wings are your thing, there's also the Wings Museum at Balcombe which gets rave reviews. Another specialist subject, toys and dolls, is catered for in Brighton, while Ditchling, in the heart of the South Downs, has a Museum of Art & Craft and the 600-year-old Priest House at West Hoathly also counts as a museum - very much a piece of social history.
In fact most of the major or historic towns in Sussex, from Chichester to Hastings and plenty in between, have their own museum, if not more than one. So wherever you're staying, they're the perfect place for a rainy day.