  Elucidating the statistical properties of extreme meteo-climatic events and
capturing the physical processes responsible for their occurrence are key steps
for improving our understanding of climate variability and climate change and
for better evaluating the associated hazards. It has recently become apparent
that large deviation theory is very useful for investigating persistent extreme
events, and specifically, for flexibly estimating long return periods and for
introducing a notion of dynamical typicality. Using a methodological framework
based on large deviation theory and taking advantage of long simulations by a
state-of-the-art Earth System Model, we investigate the 2021 North America
Heatwave. Indeed, our analysis shows that the 2021 event can be seen as an
unlikely but possible manifestation of climate variability, whilst its
probability of occurrence is greatly amplified by the ongoing climate change.
We also clarify the properties of spatial coherence of the 2021 heatwave and
elucidate the role played by the Rocky Mountains in modulating hot, dry, and
persistent extreme events in the Western Pacific region of North America.
