(270) Window of Opportunity

A window of opportunity is a period of time during which some action can be taken that will achieve a desired outcome. Once this period is over, or the "window is closed", the specified outcome is no longer possible.

About an hour before this shot was taken the sky was dull grey and rain was blowing through the wind. Two hours after I took the photo the sky was black and the rain was absolutely torrential. 
 
I, however, achieved my desired outcome and got a good hour and a half out on the bike in brilliant sunshine.