Lakes are often subject to very shifty and variable winds. On the Great Sacandaga in upstate NY, I once saw two boats on port tack pass each other in opposite directions.

Lake sailors learn to watch their masthead fly vigilantly. Not for what the wind is doing, but for what it is about to do. Lake sailors also watch the water for subtle (and sometimes not so subtle) wind shifts.

That being said, lake sailors don't have a clue about tides and currents, which adds a whole other set of variables.