The Environmental Protection Department has rated water quality at 21 beaches 'good' for this weekend, with 12 more 'fair'.

Compared with last week, water quality at Big Wave Bay, Chung Hom Kok and Pui O Beaches has been downgraded from 'good' to 'fair'.

Seven gazetted beaches - Anglers', Approach, Ting Kau, Casam, Gemini, Hoi Mei Wan and Lido - are closed to swimmers year-round because of poor water quality.

Many beaches are likely to be more polluted than their grades suggest during and after heavy rain. Bathers should avoid swimming at beaches for up to three days after a storm or heavy rainfall.

Click here to see updates on beach water quality, or call the beach hotline, 2511 6666.