Abstract. The western Mediterranean Sea suffered unprecedented marine heatwaves (MHWs) in 2022. This study focuses on the response of coastal ocean, which is highly vulnerable to global warming and extreme events that threaten the biodiversity, as well as goods and services that humans rely on. Using remote sensing and in situ observations, strong spatiotemporal variations in the MHW characteristics are observed in the coastal ocean over the last decade (2013–2022). In 2022, shallow-water moorings in the western Mediterranean Sea detected between 23 and 131 d of MHWs. While the highest MHW mean and maximum intensities were detected at the surface in French waters, the highest duration was observed nearshore at 17 m depth in the Balearic Islands. As thermal stress indicators for marine ecosystems, the highest cumulative intensity and total days were found at the surface at Tarragona, and MHW temperatures warmer than 28 °C were observed to last up to 58 d at Palma. Differences between datasets are also highlighted. In 2022, depending on the sub-regions, satellites underestimated or overestimated MHW duration and intensity compared with in situ measurements at the surface. In addition, daily data underestimate maxima reached during the extreme warm events up to 1.52 °C difference compared with hourly measurements. These results invite us to continue the efforts in deploying and maintaining multi-platform observing systems in both open-ocean and coastal ocean waters to better address the coastal adaptation and mitigation in the context of climate change.