A simulation of how the atmosphere would behave under this heating
Nasa's Spitzer space telescope has observed a far-off planet that experiences wild temperature swings.
The gas giant has an elongated orbit that sweeps it to within a few million km of its star, before taking it back out to more than 115 million km.
Spitzer saw the planet's atmosphere heat up from 530C to 1,230C in a matter of hours as it passed behind and close to its star.
The observations, reported in Nature journal, are the first of their type.
"We watched the development of one of the fiercest storms in the galaxy," said astronomer Greg Laughlin of the Lick Observatory, University of California, Santa Cruz.
"This is the first time that we've detected weather changes in real time on a planet outside our Solar System."
HD 80606b is about three times as massive as Jupiter, the biggest planet in our Solar System.
It was originally discovered in 2001 by a Swiss-based team.
The planet is located about 190 light-years away in the constellation Ursa Major.