Water quality at 21 beaches has been rated 'good' for this weekend in the Environmental Protection Department's latest gradings. Nine others are 'fair', while three are 'poor'.

Compared to last week, Big Wave Bay Beach has been upgraded from fair to good while Chung Hom Kok Beach has changed from good to fair and Butterfly Beach 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. The public is advised not to swim at these closed beaches.

As beaches are 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.

For more details, click here or call the beach hotline at 2511 6666.