Temperatures struggled to reach 15 degrees Celsius across much of the city on Sunday morning, as the observatory warned of the coldest day so far this winter.

A low of 13 degrees was recorded at the forecasters' headquarters in Tsim Sha Tsui.

It was even colder in parts of the New Territories, the observatory said.

"A strong northeast monsoon will affect the coast of southern China today. Since it will be windy, wind chill effect will be particularly significant on high ground and exposed areas. People are advised to be aware of the change in weather and keep warm when engaging in outdoor activities," it warned.

The observatory added that daytime temperatures are expected to rise this week, but mornings will still be cool.