State-of-the-art seasonal forecast systems provide predictions of unusual climate conditions in the atmosphere, ocean, land and other components of the climate. These systems are capable of predicting climate variables like temperature and precipitation months in advance. A main reason for this capability is the famous ocean–atmosphere interaction known as the El Niño Southern Oscillation (ENSO). ENSO alters the atmospheric circulation across the entire tropical Pacific and, as a result, causes teleconnections which change seasonal climates across the world. The upper ocean acts as a "memory bank" by providing long-term heat storage for the region. Our ability to predict seasonal changes is therefore strongly influenced by the subsurface ocean heat content (OHC) in the tropical Pacific.Ocean heat content (OHC) anomalies typically persist for several months, making this variable a vital component of seasonal predictability in both the ocean and the atmosphere. However, the ability of seasonal forecasting systems to predict OHC remains largely untested. A study just published in Climate Dynamics led by the CMCC Foundation—Euro-Mediterranean Center on Climate Change (CMCC) presents an assessment of the predictive skill of ocean heat content in the upper 300 m in two state-of- the-art seasonal forecasting systems.