The last time I was there this surprised me, until I realized you really don't want your bins hanging out in that heat for more than a day. Sometimes it gets pretty bad even during the same day.
The iberians probably have cheap enough labour that they needn't bother, but a high-capital low-labour sol'n is to store rubbish deep enough* that even summer daytime temperatures don't hit their surface peaks: eg https://www.molok.com/benefits-and-principles/