Chailey Heritage Foundation staged its own Woolly Hat Wednesday, asking supporters to make a donation.
The charity helps change the lives of young people with complex disabilities, providing education, care and transition services to children and young adults.
Will Folkes, Fundraising Manager, said: "I take my hat off to all our fantastic supporters all year round, but on this occasion it was a case of putting on a woolly hat. Thank you to everyone who did just that and made a donation to us at the same time. It was great to see out children and young people having fun wearing their own hats as well.
"It was a cosy day with lots of fun and smiles. Some were waring furry woollies, some had crazy novelty hats, while pupils and staff wore their own stylish knits."
Bluebell Vineyard Estates near Uckfield was among the companies taking part. BNI Vanguard Horsham - a business group which meets on a Wednesday morning - also joined in the fun.