An extreme heatwave took place in East Antarctica in March 2022, which registered the most anomalous temperatures above local climatology ever recorded. The heatwave resulted from a highly unusual weather pattern which produced strong northerly winds and imported warm and moist air from Australia. Weather forecast models skillfully predicted the heatwave up to 8 days in advance. While the heatwave took place soon after the record sea ice minimum of February, Southern Ocean sea surface temperature anomalies had a minimal impact on the magnitude of the heatwave. We have found that a widely used climate model cannot simulate heatwaves of this magnitude, but when the model’s winds in the free atmosphere are nudged toward observations, the model can simulate a heatwave closer to observations, suggesting model improvements in atmospheric circulation variability would lead to better heatwave simulation. To address the impact of climate change, we have re-run the model simulations, nudging to the same winds but under past and future anthropogenic forcing. We find that the heatwave was made 2°C warmer by climate change, and future end of century heatwaves to be 5–6°C warmer, suggesting the possibility of near-melting temperatures over the East Antarctic ice cap during extreme heatwaves.