Storm Doris is expected to move on quickly, with the worst of the weather gone by Thursday evening.
Monday's temperature was recorded at Kew Gardens, west London, where visitors enjoyed temperatures 10 degrees warmer than Milan at 8C.
The cloud of hot air is making its way over the Atlantic Ocean from Florida and parts of the Caribbean.
The Met Office says Friday will be particularly cold with temperatures of 2-3C.
From the "lightest of falling dandruff" to "snowing onto my face right now", Londoners were quick to let the rest of the capital know.