To take an opportunity to do something when the
time and conditions are near perfect or available.
From agriculture, when farmers gather the long grass growth of summer to
dry it to produce hay as winter feed for animals; The best
time to cut and dry the hay is during sunny days.
A:"There's a sale at K-mart this week - You wanna see if the have
something for your sister's
birthday?"
B:" Sure - Might as well make hay while the
sun shines, and get her something at cut price!"