Rather cool and rather dry.

Average temperature = 9.9°C; diff from climate av: -0.1°C
Average humidity = 77%
Average dewpoint = 5.6°C
Average barometer = 1015.0 mb
Average windspeed = 6.2 mph
Average gustspeed = 9.1 mph
Average direction = 297° (WNW)
Rainfall for month = 26.6 mm (-28mm)
Rainfall for year = 371.2 mm (+74mm)
Maximum rain per minute = 0.6 mm on day 21 at time 13:42
Maximum temperature = 23.3°C on day 08 at time 14:47
Minimum temperature = 0.6°C on day 14 at time 23:31
Maximum pressure = 1025.8 mb on day 03 at time 23:08
Minimum pressure = 1000.8 mb on day 18 at time 08:50
Maximum windspeed = 27.6 mph from 360°( N ) on day 31 at time 16:14
Maximum gust speed = 44.9 mph from 360°( N ) on day 31 at time 14:04
Maximum heat index = 25.2°C on day 08 at time 17:29
Avg daily max temp :13.9°C
Avg daily min temp :5.7°C
Growing degrees days :60.0 GDD
Total windrun = 3948.4miles
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Daily rain totals
-----------------------------------
00.6 mm on day 1
01.6 mm on day 2
00.8 mm on day 19
00.6 mm on day 20
09.0 mm on day 21
03.6 mm on day 22
05.2 mm on day 25
01.2 mm on day 26
00.4 mm on day 30
03.2 mm on day 31

Summary for May 2016

Temperature (°C):
Mean (1 minute)  13.8
Mean (min+max)   13.8
Mean Minimum     8.2
Mean Maximum     19.5
Minimum          0.0 day 19
Maximum          25.3 day 08
Highest Minimum  15.0 day 09
Lowest Maximum   13.5 day 25
Air frosts       0

Rainfall (mm):
Total for month  60.3
Wettest day      14.7 day 10
High rain rate   21.6 day 27
Rain days        12
Dry days         19

Wind (km/h):
Highest Gust     72 day 11
Average Speed    5
Wind Run         2766.0 km
Gale days        0

Pressure (hPa):
Maximum          1033.4 day 15
Minimum          1004.7 day 11

Days with snow falling         0
Days with snow lying at 0900   0

Summary for May 2016 in Watford

Temperature (°C):
Mean Minimum 9.1
Mean Maximum 19.4
Minimum 2.5 day 03
Maximum 27.8 day 08
Highest Minimum 14.5 day 09
Lowest Maximum 12.2 day 31
Air frosts 0

Rainfall (mm):
Total for month 48.9
Wettest day 20.7 day 23
High rain rate 50.4 day 23
Rain days 10
Dry days 21

Pressure (mb):

Maximum 1031.8 day 03
Minimum 1011.9 day 18

Days with snow falling 0
Days with snow lying at 0900 0

More on my blog http://alalchan.tumblr.com/post/145330865276/watford-weather-may-2016