Coastal sea level extremes have widespread impacts on coastal systems, ranging from infrastructure damage due to coastal flooding to the exposure of coral reef systems and mangrove dieback during low water level extremes (e.g. the low sea level event in the Gulf of Carpentaria in 2016). Sea level extremes are driven by atmospheric and oceanic processes such as astronomical tides, storm surges and subseasonal to seasonal variability associated with climate drivers such as the El Niño-Southern Oscillation. Some of these processes are potentially predictable ahead of time, such as the tides (years) and climate drivers (weeks to months). This predictability suggests that it may be possible to provide early warning of upcoming sea level extremes. Here, we discuss ongoing coastal hazards work as part of the Australian Climate Service (ACS) to develop such an early warning system by combining harmonic tide predictions with sea level forecasts from the Bureau of Meteorology's dynamical subseasonal to seasonal forecast model. We discuss the design of this sea level prediction system and evaluate its skill across the Australian tide gauge network. Early results are promising, indicating potential for providing valuable information to support decision making by coastal managers on seasonal timescales.