Marine (MHW) and atmospheric heatwaves (AHW) are extreme thermal events of growing ecological relevance for intertidal communities (Stillman et al., 2025). Using in-situ data from the ISPRA monitoring network across 34 Italian coastal stations (2010-2025), we identified 1,577 MHW and 6,826 AHW events (Hobday et al., 2016; Perkins & Alexander, 2013, respectively). Unsupervised classification identified three recurring event typologies: Dynamic, short and moderately intense events; Pulsed, short duration with rapid onset; and Persistent, long-lasting. The most ecologically relevant finding was the widespread co-occurrence of marine and atmospheric heatwaves: 73.6% of MHW overlapped with at least one AHW at the same station, and the annual number of overlap days increased markedly over the study period (+13.5% yr⁻¹). This increasing concurrence likely amplifies thermal stress through air–sea heat exchange processes (Paredes-Fortuny et al., 2025; Barkhordarian et al., 2025). Co-occurrence patterns also varied seasonally, indicating that organisms experience distinct thermal regimes depending on when compound events occur. These patterns (event typology, co-occurrence dynamics, and seasonal exposure) define the parameter space for realistic laboratory simulations. Based on this framework, we developed a library of 28 data-driven thermal trajectories representing realistic marine, atmospheric and compound heatwave scenarios. Each trajectory incorporated event characteristics and, for compound scenarios, overlap properties including duration, onset offset, and aerial exposure fraction, stratified by season and event typology.  By translating long-term climate observations into a library of data-driven thermal trajectories, this framework bridges climate monitoring and experimental ecology. Capturing the temporal complexity of observed heatwaves, rather than relying on arbitrary warming treatments, provides a mechanistic foundation for predicting how intertidal organisms and communities will respond to increasingly frequent compound climate extremes.