maciec, it probably depends on a day-to-day basis on the actual temperature. Most pools are heated, hence you can notice a big difference in the temp when you get out of the water. Anything close to 75 will probably still be quite pleasant (if it's sunny), but 70 or just below may be a bit chilly (it also depends to a certain extent where you're from - you'll find us Brits still charge into the water in Florida at ANY time as it's MUCH warmer than back home!).