Hello and welcome. They stay open in the sense that they are cleaned and maintained all year and, aside from the bottom large pool that for health and safety law reasons has to have a life guard whilst open, they are not locked. Officially however, they are usually open from late may to late October. They aren't heated and so tend to be chilly outside of these times but some do use them. My kids go in during warmer Easters and my husband and his friend once braved a width on New Year's Day! Not advisable! People do climb the gate to the big pool at the bottom outside of official opening times too.