Climatological hot extremes (HE) can be classified as dry hot extremes (DHE) and humid hot extremes (HHE). The latter occur as a combination of high temperature and high humidity and are particularly harmful for human health. Both events pose ecological and socioeconomic risks and are expected to aggravate in the future. However, the physical processes that cause these events are difficult to observe and unravel, and they become even more uncertain under climate change. A good understanding of how DHE and HHE are caused would increase our ability to predict them and anticipate their impacts. CausalHeat will explore: (i) what causes these events, (ii) how they propagate in time and space, and (iii) how the mechanisms causing them will respond to climate change in the future. We will use novel causal discovery methods that quantify causality from observational data, concentrating on the spatiotemporal origins and propagation of the moisture and heat leading to these events. As such, CausalHeat will provide new insights into the different mechanisms causing hot extreme events, as well as situations with temporally cascading occurrences, in both historical and future periods. This will help enhance societal preparedness to the ongoing exacerbation of these events.