Kate Hudson's Red Hot Reveal

Kate Hudson is great at surprises ... 'cause check out the awesome one she was hiding under long winter coat in NYC. Daaammmmmnnn!

Kate looked all conservative as she walked into the Greenwich Hotel Wednesday night, but once inside ... her super low-cut red jumper was everything.

We'll give her a pass for the boring blue coat, since it kept that cleavage-baring outfit so pristine.

Just a thought -- Kate's looking hotter than ever these days. No?