Impact of extreme temperatures on emergency department visits: A multicenter study in Catalonia (2020-2025)

To analyze the relationship between extreme temperatures and hospital emergency department (ED) visits in Catalonia (Spain), assessing their impact on workload and case severity.

We conducted a retrospective, multicenter, ecological time-series study with 8 public hospitals serving a population of 4.7 million people. ED visits from January 2020 through August 2025 were analyzed according to triage level. Daily mean, minimum, and maximum temperatures were obtained from 198 weather stations of the Catalan Meteorological Service and assigned to each hospital by proximity. The association between temperature and hospital admissions was evaluated using distributed lag nonlinear models (DLNM) with quasi-Poisson regression.

More than 4.55 million visits were recorded during the study period, with a mean of 275 daily visits per hospital; 47.2% of patients were triaged as levels I, II, or III. Two peaks in workload were observed: winter (October-December) and summer (May-August). Maximum temperature showed the strongest association with admissions, with increases of 42.8% in total visits and 37.7% in level 1 patients at the most extreme percentiles vs reference values.

Extreme temperatures increase ED activity, particularly among the most severe cases. These findings support the need to strengthen summer-specific care plans and integrate emergency indicators into surveillance systems to address the health effects of climate change.