I've noticed since riding a lot of north/south routes in London (mostly inner east side) that in the afternoons when cloudy and threatening to rain there is a northerly breeze. On clear warm day it's southerly... today (rather overcast all day and threatening in the early afternoon) I tried my theory and took a south/north route - I got a tail wind all the way home.. 
Co-incidence?
Just thought I'd put it out there anyway.

Co-incidence?
Just thought I'd put it out there anyway.