Yesterday was the wettest April day in Morden for 15 years. Much of the rain fell today (30th) but a 'rain day' runs for 24 hours from 0900UTC.
The 17.5 mm was eclipsed by the 27.8 mm that fell on the 1st April 1993 and the 31.2 mm that was recorded on the 29th April 1991. On the 10th April 1878, a total of 99 mm of rain fell at Haverstock Hill (Highgate).
Over the last 20 years, April has proved, on average, to be the wettest Spring month, but this year it looks as if March will take the honours.