Some heavy daily rainfall stats for Luton
 

In the composite record for Luton (1901- ) the wettest
rainfall days for each month we

Jan 36.8 28th in 1927
Feb 36.0 16th in 1919
Mar 26.0 27th in 1916 (a remarkable snowstorm -
one that my Dad would talk about to his dying
day even though he was not quite five at the time)
Apr 51.2 3rd in 2000
May 74.8 29th in 1992 (two severe thunderstorms;
98.4mm in 48h)
Jun 88.0 28th in 1906 (appears to have a frontal event)
Jul 49.0 10th in 1959
Aug 67.3 12th in 1938
Sep 57.1 15th in 1968 (78.2 in 24h straddling two
rainfall days in Sep 1998)
Oct 50.2 9th in 1987
Nov 36.5 11th in 1906
Dec 48.0 1st in 1919

Falls of 25mm and 50mm have been distributed thus:
Month 25 50
Jan 4 0
Feb 3 0
Mar 2 0
Apr 8 1
May 8 1
Jun 22 3
Jul 32 0
Aug 18 3
Sep 17 2
Oct 19 1
Nov 11 0
Dec 9 0

Which gives us just under three 25mm events every
two years on average, and one 50mm every ten years.
However, there was no 50mm between Aug 1939 and
Sep 1968.

(c) Philip Eden