heat lightning

1 7.0

Bright flashes in the far sky at night with no nearby thunder, often on hot evenings

noun
/hit ˈlaɪt.nɪŋ/

: relámpago de calor

July night thunder, monsoons walking across the far horizon, illuminated by heat lightning.
a flash of heat lightning
heat lightning on the horizon

Examples

It was balmy still, and though the sky was clear, the horizon flashed with heat lightning, and the elm trees moved their limbs about in the warm wind.

Fiction book (1999)
In the distance, we both watched a flash of heat lightning, which Paul mistook for a storm heading our way.

Fiction book (1990)
After dinner, he strolled on the common, watching the heat lightning flicker beyond the hills.

Fiction book (1993)
Mr. Powers' summer storm was moving in off the bay; the sky groaned and heat lightning flashed across the brick factories.

Fiction book (1990)
After dinner, we sat outside, enjoying the warm evening air while watching the beautiful flashes of heat lightning light up the horizon.
On a hot summer night, the distant heat lightning illuminated the clouds, creating a stunning display without any accompanying thunder.
We enjoyed our picnic as occasional flashes of heat lightning flickered in the sky, hinting at a storm far away.

Synonyms

lightning

vsheat lightning

512 1.0

A sudden bright flash in the sky during a storm caused by electricity

is limited to distant horizon flashes seen without thunder on hot nights

sheet lightning

vsheat lightning

6.2

A wide, soft flash that lights the sky from distant lightning behind clouds

is the specific night horizon flash seen without thunder and usually on hot evenings

Surface Forms

heat lightning singular

heat lightnings plural

Morphology

heat + lightning

The meaning is compositionally 'lightning associated with heat', so a B1 learner who knows 'heat' and 'lightning' would likely infer it refers to lightning seen on hot evenings. However, the precise meteorological nuance (distant flashes with no audible thunder) is a technical detail not predictable from the parts alone, making the expression only partially transparent.

Etymology

Heat lightning comes from warm summer nights when lightning from far-away storms flashes in the sky but you can't hear thunder. Because these quiet flashes often happen on hot evenings, people pictured the bright light as coming from the heat and called it heat lightning, so it means 'lightning you see but don't hear'.