The London Frost Fairs, were festivals held out on the ice when the River Thames froze over. Most of these fairs were in January or February, and the last of them took place in 1814.
Research:

Behind the Scenes Minis: Dorothy Everywhere
20:00

Dorothy Crowfoot Hodgkin’s Crystalline Chemistry, Part 2
43:14

Dorothy Crowfoot Hodgkin’s Crystalline Chemistry, Part 1
38:04