I've talked of lots of guys storing ammo in a garage or shed for decades and not having issues. Sealed in ammo cans so no humidity swings but temperatures ranging from -30'C to +30'C.
I've also heard stories about guys in Arizona or Texas having ammo get wonky after a few years stored in a hot shed or garage. But we'd be talking about regular daytime highs of +45'C
I see no issue with +7'C so long as you control humidity. Sealed ammo cans with good gaskets, not opened on a regular basis, add some desiccant packs for good measure. One guy I know throws oxygen absorbers in vacuum sealed bags with his ammo for long-term storage.