The Environmental Protection Department has rated water quality at 13 beaches 'good', 12 'fair' and eight 'poor' for this weekend.

Compared with last week's gradings, Kwun Yam, Lo So Shing, Lower Cheung Sha and Turtle Cove Beaches have been upgraded from fair to good, and Big Wave Bay Beach upgraded from very poor to poor.

Chung Hom Kok and South Bay Beaches have changed from good to fair, and Cafeteria New, Golden and Silver Mine Bay Beaches have gone from fair to poor.

The Department said the changes are generally within the normal range of fluctuation of the bacteriological water quality of the beaches.

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