Mom's basement was damp once in 20+ years in the home. The weather was typical, not super wet. They fussed with repairs a bit and the sump pump ran regularly. A few weeks later the local utility found a water main break. I wonder (but can't prove) if the water main was leaking for a while, causing the wet conditions.

Do you have a sump pit/pump? If not, adding one might reduce the odds of future standing water in the cellar.

Thanks Quip! No water lines anywhere near it (it's detached from the house & at least 30' away.) By the time I got a sump pump down there, not enough water left for it to work. I'd left the door open, so suppose a few 90+ degree days is drying it out.
Suzi