Hi ,wallows are pretty much essential in hot weather for pigs . Cools them down since they have no sweat glands and doubles as a mud spa for wifey??
Not just cooling, the mud on their skin acts as a sunblock and helps them not get sunburnt quite so much.
Serious welfare issue. Pigs need wallows in hot weather. And fresh drinking water besides. (They will pee in their wallow and they won't drink soiled water. Muddy yes, no worries. Peed or pooped in, no.)
When we get a drought period we have a rota for 3-times-a-day checks to top up the pigs' wallows and drinkers.