Mid June 1903 was exceptionally wet in the south of UK with the Camden Square station in London recording 6.43 inches of rain in the period from the 9th to the 19th of June 1903From 1pm on the 13th to 11.30pm on the 15th, rain fell continuously for 58 hours and 30 minutes giving a total of 3.44 inches for that period.
Over 1 inch of rainfall fell on the 13th, 14th and 15th. The maximum temperature on the 19th was just 10.4C, 9.4C at Greenwich
Rainfall totals for June 1903Carshalton Sewage Works: 8.91 inchesBrimstone Park: 8.1 inchesHayes: 7.39 inchesBroxbourne: 6.84 inches
It wasn't wet everywhereMarkree Observatory: 0.7 inchesDunderave, Bushmills: 0.72 inchesCreggan Reservoir: 0.87 inchesHorncastle: 0.88 inchesLincoln: 0.91 inches
I've read about that one - wasn't that one a case of, "rain from the east two days at least".