I was looking up sunrise/sunset data for Nottingham, and this website gives a fascinating data table for what weather to expect in this part of the world.
Nottingham, United Kingdom – Solar energy and surface meteorology
|Clearness, 0 – 1||0.32||0.34||0.37||0.39||0.41||0.39||0.41||0.41||0.38||0.34||0.30||0.30|
|Wind speed, m/s||7.70||7.31||7.05||6.01||5.49||5.07||5.04||5.36||6.11||6.73||6.97||7.39|
|Wet days, d||17.8||14.6||16.3||14.7||14.8||13.2||12.1||14.0||12.9||15.1||16.3||16.7|
These data were obtained from the NASA Langley Research Center Atmospheric Science Data Center; New et al. 2002
It’s interesting how little variation there is throughout the year. Clearly sunshine and temperature change with the seasons with the best insolation – the sunshine that falls on the ground – in May, June and July. So a better early part of the year is good for the for solar panel than sunshine during the school holidays.
But for the other data there’s really very little change. The average rainfall per month varies from 47-60. Wet days are more or less the same every month, with only a five day difference. And the wind speed average barely changes at all.