I would base the calculation for expansion on the worst case, which would be the highest & lowest outside air temperatures in your area. The only thing I'd skip is the addition of 20 degrees for conduit in direct sunlight. This is a conservative approach, but unless you're planning a very long run, one expansion fitting should do the trick.
In the area I live in, for conduit exposed to the sun, I come up with a calculation of about 7 feet before an expansion fitting is needed.
Expansion & contraction is a real problem, I've seen plenty of installations with busted couplings or the conduit pulled apart exposing the conductors.
