May 1989 was a superb month with a glut of sunshine, only July 2006 was sunnier than May 1989 since August 1995 for England and Wales with 266.3hrs

May 1989 was a mostly dry month dominated by high pressure. It was also a warm month with a CET of 13.0 making it the warmest May jointly with  1970 since May 1964, with maxima sometimes 25C+ (29.4C at Heathrow on the 23rd) Thunderstorms broke out on the 19th and 24th especially in parts of Yorkshire, where there were flash flooding.

Glasgow
Mean Max: 16.0C Rainfall: 30mm (28%) Sunshine: 225hrs (120%)

Manchester
Mean Max: 17.7C Rainfall: 32mm (53%) Sunshine: 258hrs (139%)

Birmingham
Mean Max: 18.7C Rainfall: 15mm (27%) Sunshine: 253hrs (138%)

Heathrow
Mean Max: 21.0C Rainfall: 12mm (25%) Sunshine: 310hrs (158%)

Belfast
Mean Max: 16.0C Rainfall: 30mm (54%) Sunskine: 249hrs (135%)

Plymouth
Mean Max: 18.3C Rainfall: 6mm (10%) Sunshine: 313hrs (142%)

Cardiff
Mean Max: 18.5C Rainfall: 10mm (16%) Sunshine: 279hrs (139%)

CET and rainfall trackometers

1.    13.1     0.1
2.    12.2     0.1
3.    12.8     0.1
4.    13.2     0.1
5.    13.5     0.1
6.    13.1     0.1
7.    12.8     0.1
8.    12.8     0.2
9.    12.5     0.2
10.  12.2     0.6
11.  12.0     4.8
12.  11.7     7.9
13.  11.5     8.3
14.  11.6     8.3
15.  11.7     8.8
16.  11.7     8.8
17.  11.7     9.4
18.  11.9     9.7
19.  12.2     9.9
20.  12.4     10.2
21.  12.7     10.3
22.  12.9     11.1
23.  13.1     13.0
24.  13.3     18.9
25.  13.3     18.9
26.  13.3     18.9
27.  13.2     18.9
28.  13.2     18.9
29.  13.2     18.9
30.  13.1     18.9
31.  13.0     20.7

I remember the MCS that moved up the western part of UK on the morning of 19th May, we basically had a 2 and 1/2 hour thunderstorm here. 

2 and a 1/2 hour thunderstorm........ struggling to even get a day with just a single rumble of thunder these days.

Don't remember May specifically, but I do recall that whole summer having a lot of good weather (I've got plenty of specific memories, and they all seem to have dry/sunny weather in them)

Lets hope this summer is good after what is turning out to be an excellent May this year.

I too remember May 1989 as being a pretty good month with an abundance of warm & sunny weather. I particularly recall Saturday 20th May as it was the day of the F.A and Scottish Cup Finals; it was a glorious day, even if my team lost the Scottish final!

Great write up Kevin as always I remember 89 well, was doing exams at school , and then leaving school early June. I remember the terrific thunderstorm, then having a exam next day late morning, also turned very hot and humid. Defo 89 was a good summer ! like others said a classic one and forgotten one.