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The weather in Hong Kong will be foggy on Friday, with visibility below 500 metres (1640 feet) in some areas, as marine authorities urged vessels to proceed at safe speeds and exercise extreme caution.

The Hong Kong Observatory forecast a foggy morning on Friday as a southerly airstream affected the coast of Guangdong. The visibility at Waglan Island fell below 500 metres.

“Under the influence of a southerly airstream, it will be hot during the day over the coast of Guangdong today. The weather will be relatively humid and foggy,” it said.

Friday was forecast to be mainly cloudy with a few showers, and temperatures at between 21 and 29 degrees Celsius (70 to 84 Fahrenheit). It will be hot in the afternoon with chances of isolated thunderstorms later in the day.

The Observatory said a cold front would edge southwards towards the coast of southern China on Friday, bringing a few showers and thunderstorms over the region, while it was expected to move across the coastal areas later in the day.