Blindingly means so brightly or obviously that it overwhelms. Blindingly bright, blindingly obvious, blindingly fast.
Blindingly obvious is much the commonest use, and it is usually said by somebody who has only just seen it. The literal sense belongs to light strong enough to hurt. It attaches to a small set of adjectives and to almost nothing else.
1adverbblindinglySo brightly or obviously that it overwhelms.
“The snow was blindingly white in the morning sun.”
blindingly is a degree.
From blinding + -ly.
Etymology from Wiktionary, CC BY-SA