The observatory said on Friday that it expects a trough of low pressure to continue bringing unsettled weather to Hong Kong over the weekend.

At 4:25am on Friday, the observatory issued its first Red Rainstorm Warning signal of the year, triggering the suspension of all morning and whole-day school classes.

The red signal was replaced with an amber warning at 7:05am, before this was cancelled at 7:40am.

The observatory’s director, Cheng Cho-ming, said occasional heavy showers and thunderstorms are expected over the weekend and urged people to avoid going to mountain streams as there may be flash floods.

“For the time being, we would say that the weather will still be unsettled, so beware that the weather may change anytime. So be prepared for that,” he said.

Cheng also reminded students who are scheduled to take DSE exams on Saturday to keep tabs on the latest weather situation.

He noted that while different weather forecast systems have come up with different predictions about the weather over the weekend, they all predict that it will improve on Monday, with northerly winds pushing rain bands further south and away from the city.

He said temperatures are expected to drop gradually on Sunday to around 21 degrees at night, before dipping to around 19 degrees on Monday morning.

The trough of low pressure over southern China also brought heavy rain to places including Guangzhou and Macau during the week.

Authorities in Macau and Guangzhou on Tuesday night ordered schools to suspend classes the following day.

When asked whether the observatory could issue rainstorm warnings further in advance in future, Cheng said that would have to depend on the weather situation.

“Different places may have different considerations. And also, as a matter of fact, different places may have different rainstorm situations. For example, in the past couple of days, our rain was not particularly heavy. Occasionally, we received 20 to 30 millimetres of rain in one hour, but most of the time, it was less than that. So for us, I think having just issued the amber rainstorm [signal] is okay,” he said.