South Wales Police says the A465 is closed between Aberdulais and Resolven, after a serious crash.
Diversions are in place via the B4242.
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Mostly dry tonight. Warm sunny spells tomorrow, with isolated thunderstorms.
The RNLI has warned of the dangers of going into cold water after a teenager was dragged unconscious from the sea by a friend.
Real Madrid won another Champions League title, beating a shell-shocked Liverpool side 3-1 in Kiev.