We would like to acknowledge project AquaMMIn (MAR-02.01.01- FEAMP-0038), co-funded by Portugal (2020) and the European Union through Mar2020, the Operational Programme (OP) for the European Maritime and Fisheries Fund (EMFF) in Portugal. We also acknowledge financial support to CESAM by FCT/MCTES (UIDP/50017/2020+UIDB/50017/2020+LA/P/0094/2020), through national funds, to L'Oreal/FCT/UNESCO for the prize L'Oreal Medals for Women in Science Portugal awarded to D.M., to FCT/ MEC through Scientific Employment Stimulus – Individual Call 2018 (CEECIND/01250/2018 to DM) and PhD scholarship call 2021 (2021.04675.BD to JFF), to Do*MAR Doctoral Programme [PD/BD/127989/2016 to DJ] and to the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020.

Raw data on wet weight and upper thermal tolerance limits (CTMax) of the ragworm Hediste diversicolor collected at Ria de Aveiro (Portugal) and subjected to a combination of different temperatures (24, 27 and 30 ºC) and salinities (20 and 30) after 29 days of acclimation. Wet weight data was obtained post-CTMax assay.