As part of the month-long #whenitrainsitpours social media drive, Fuller’s will provide a live broadcast weather monitor showing a windowpane via Twitter and Perisope.
Updates will appear on Twitter timelines prompting followers to tweet in as soon as they notice rain on the Periscope window. They will then receive a free pint of London Pride as part of the exchange.
Fish, who will appear in video clips as part of the campaign, which was designed in collaboration with advertising agency The Corner and creative media business UM London, said: "This is such an inspired idea.
"February can often be one of the dreariest months of the year with the short days and wet weather, so a free pint of London Pride will certainly brighten up people's days… I’ve seen some very rare atmospheric phenomena, but even in all my years as a weatherman, I’ve never seen it rain beer."
The ex-BBC weatherman hit the headlines in the 1980s after telling viewers that there would not be a hurricane the night before 1987’s great storm.
In December 2016, Fuller's took pity on Southern Rail commuters as they battled strikes by offering them a choice between one free beer, cider, soft drink or glass of wine on receipt of their train ticket.