The countries of Southeast Asia are highly exposed and vulnerable to the effects of climate change and climate variability. This article provides an overview of the current understanding of future climate change and sea level rise in the region. It also provides an overview of weather and climate characteristics and past trends. In recent decades, the mean surface air temperature has risen, by about 1.0–1.5 °C between pre-industrial period (1850–1900) and 2020. Extreme heatwaves and intense precipitation events have also become more frequent, which is largely attributed to human activities that have led to increased greenhouse gas concentrations in the atmosphere. Sea levels are rising at a rate of 4.0–8.2 mm per year, which has a significant impact on low-lying areas such as the Mekong Delta. Climate projections show that the tendency for extreme weather events and sea level rise will increase with each degree of global warming. The intensity and frequency of weather and climate extremes will increase significantly with warming above 2.0 °C compared to the conditions expected at 1.5 °C. Sea level rise will also be greater under the same scenario. Countries in the region face increased climate risks, as the current Nationally Determined Contributions (NDCs) under the Paris Agreement are not sufficient to curb warming to below the 1.5 °C target. Instead, they are expected to lead to warming of 2.5–2.9 °C above pre-industrial levels by the end of the twenty-first century.