I live in a desert area which is fairly similar to their native environment (though much colder), and the humidity is generally around 30%. This is perfectly fine for them, it doesn't need to be drier. Where leos live, heavy fog often blankets the area in the morning, with humidity climbing over 80% at times--this lifts as the day breaks. Leos also spend the day in relatively humid burrows. They're designed to go from high humidity to low humidity conditions, but absolute extremes of either are not necessary (they don't require humidity over 80%, nor under 30%, at any time).
The humidity here usually fluctuates between about 80% and 30% over the course of a day, sometimes becoming dryer, other times more humid (usually if it rains, which is infrequent even at this time of year).
Those from a desert will understand just how dry 30% humidity actually is.
Anyone not used to it will get nosebleeds and chapped lips in no time.