TL;DR: It means that it was very hot. The addition of ‘hinges’ to the common English idiom ‘hot as hell’ provides emphasis via alliteration. (Alliteration for emphasis is the reason we go to hell in a handbasket rather than some more practical mode of conveyance.)
Hell is traditionally depicted with doors or gates, which would naturally have hinges. In the Bible, Jesus says to Peter:
And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
Gospel of Matthew 16:18. Authorized Version.
In Paradise Lost:
On a sudden open fly,
With impetuous recoil and jarring sound,
Th’ infernal doors, and on their hinges grate
John Milton (1674). Paradise Lost, Book II, lines 879–882.
Most famously, in The Inferno, Dante and Virgil pass through the gate of hell, above which is an inscription:
I AM THE WAY INTO THE CITY OF WOE.
I AM THE WAY TO A FORSAKEN PEOPLE.
I AM THE WAY INTO ETERNAL SORROW.
SACRED JUSTICE MOVED MY ARCHITECT.
I WAS RAISED HERE BY DIVINE OMNIPOTENCE,
PRIMORDIAL LOVE AND ULTIMATE INTELLECT.
ONLY THOSE ELEMENTS TIME CANNOT WEAR
WERE MADE BEFORE ME, AND BEYOND TIME I STAND.
ABANDON ALL HOPE YE WHO ENTER HERE.
These mysteries I read cut into stone
above a gate. And turning I said: “Master,
what is the meaning of this harsh inscription?”
Dante Alighieri (1320). The Inferno, Canto III, lines 1–12. Translated by John Ciardi (1954).
The allusion to the gate of hell, with its inscription ‘Abandon all hope, ye who enter here’, reminds the reader of The Green Mile of the hopeless situation of the inmates on death row in Cold Mountain State Penitentiary.
Among the locations for the 1999 film of The Green Mile was the (then recently closed) Tennessee State Penitentiary in Nashville, where:
Behind the silent walls, however, was a world unto itself, as inmates learned when they walked into the cellblocks in the penitentiary’s early years. They passed under a large sign that loomed overhead, stating “Abandon all hope, ye who enter here,” a jarring reminder that they were the property of the state for the foreseeable future.
Yoshie Lewis and Brian Allison (2014). Tennessee State Penitentiary, p. 7. Charleston: Arcadia.