Historical climate conditions were examined to determine whether climate information could improve decisions concerning the seasonal maintenance and operations of regional outdoor swimming pools in heavily urbanised northeastern Illinois. Key weather-sensitive issues defined for pool companies concern time periods for maintenance (including pool painting), weather limits to pools being open, and hot days which extend hours of pool operation. The specific conditions included the frequency of spring and fall painting periods (defined as dry conditions for two or more days with Tmax ≥18 °C (65 °F) and Tmin ≥ 4 °C (40 °F)); summer inclement weather days (days with precipitation ≥ 2.54 mm (0.10 inch) with not more than 2 consecutive hours of dry conditions during open swimming hours and/or Tmax ≤ 21 °C (70 °F)); and hot days (Tmax ≥ 32 °C (90 °F)) were examined.

Climatic records for the region going back 42 years revealed that there were nearly twice as many fall painting periods as those in the spring, indicating that greater emphasis should be placed on pool painting after the swimming season. The average number of inclement weather days was more than twice the number the company budgeted for at the beginning of each swimming season. Plans to extend swimming hours on hot days involves a risky decision since the number of hot days varies dramatically from year-to-year in the Chicago region. Studies showed that winter negative sea-surface temperature anomalies in the central Pacific were related to an above average number of spring painting periods. Also, a higher number of hot summer days occur following El Niño-classified winters. Results reveal that decision-makers in the swimming pool management industry can improve several management decisions by including climate information.