It’s a well-known fact that Las Vegas is located in the middle of a desert and it can get pretty hot. When you are in such a warm environment, the water in a pool will feel much colder than it actually is.
In cities like Las Vegas, with low humidity, it takes much longer for pools to warm up, and the water loses its temperature much faster as well.
It takes a long time for water in low-humidity cities to warm up, and if new, cold water is constantly added, it will take even longer.
In cold environments, our bodies work much harder to stay at the right temperature, which is why we can suffer from hypothermia if exposed to extreme cold.
Your body loses heat through evaporation, and since you are swimming in a Las Vegas pool, evaporation will happen quickly, meaning you will lose heat fast and get really cold.
The good news is that Vegas is quite warm during most months of the year, so lounging poolside, you will warm up quickly if you get chilled.