Most natural cellars have some degree of temperature change from winter to summer. So a little bit of gradual fluctuation with the seasons, and having it a couple of degrees warmer in summer than winter probably wouldn’t do much harm. But you want to avoid repeated/rapid temperature changes, storing it too warm for an extended period, and all the other things you might get in a normal room (sunlight, vibration, low humidity…).
Of course, if you’re storing for investment/resale, then you need to be able to show pristine conditions if you want to get the best price in future, which is partly why the professional storage companies are so widely used.
TWS has a bit of general storage guidance here: