The incidence of heat-related illnesses from midnight to 10 a.m. has skyrocketed by more than 900 percent over the past decade, outpacing the growth rate of daytime cases.

According to the Korea Disease Control and Prevention Agency’s annual report released Tuesday, the number of patients recorded between 6 a.m. and 10 a.m. soared by 1,225 percent, from 20 cases in 2011 — the first year of the monitoring system — to 265 cases last year. The number of patients between midnight and 6 a.m. increased by 320 percent, from 10 to 42 cases.

Overall, the combined figures for midnight to 10 a.m. revealed a 923 percent increase, rising from 30 cases in 2011 to 307 cases in 2023.