At the depth and temperature of Hourglass Cave, water that percolates through the overlying rock does not dry between visits.

The floor of many passages is a saturated clay mixture that coats everything it touches and that makes traction difficult on slopes and in climbs.

Cavers exploring Hourglass wear the kind of protective gear that extended cave trips require — full-body coveralls, rubber boots, helmets — and they still come out covered.

The temperature stays close to the freezing point throughout the cave, year-round.

Not below freezing — the caves of the Rocky Mountain region do not typically drop to ice-forming temperatures in their deep sections — but cold enough that extended time in the cave, without sustained physical activity to generate body heat, produces genuine risk of hypothermia.