Given the strength of relationship between past GSAT and warming trends at lake surfaces  and projected increases in heat waves, surface water temperatures are projected to continue to increase . Mean May to October lake surface temperatures in 46,557 European lakes were projected to be 2.9ºC, 4.5°C and 6.5℃ warmer by 2081-2099 compared to the historic period  under RCP2.0, RCP6.0 and RCP8.5, respectively . Under RCP2.6, the average intensity of lake heat waves increases from 3.7ºC to 4.0°C and the average duration from 7.7 to 27.0 days, relative to the historic period . For RCP8.5, warming increases to 5.4ºC and duration increases dramatically to 95.5 days  .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report