The Weather of May 1997

    The weather in May was on the whole near normal. The mean temperature of 26.1 degrees was only 0.2 degrees higher than the normal figure. The month's total rainfall of 300.8 millimetres was 15.9 millimetres below normal whilst the accumulated rainfall since 1 January, 625.1 millimetres, was only one per cent above normal. A Rainstorm Red Warning and a Landslip Warning were issued on 8 May while Flood Warnings were issued on seven occasions in the month.

    The weather was generally fine on the first two days of the month. It became cloudy on 3 May and heavy rain with thunderstorms developed later in the evening. The southern part of Hong Kong Island recorded over 150 millimetres of rainfall on the morning of 4 May. Three trees and a scaffolding at different locations collapsed on 5 May injuring four persons. Occasional heavy rain and thunderstorms continued to affect Hong Kong during the next couple of days.

    A Rainstorm Red Warning was issued on the morning of 8 May. Over 200 millimetres of rainfall were recorded between 8 a.m. and 11 a.m. in Tsuen Wan on 8 May. A private housing estate there suffered an electricity blackout for nine hours caused by the rainstorm. There were also 26 reports of landslips and 15 reports of flooding. A house under demolition in Yuen Long collapsed, killing one person and injuring another.

    Winds strengthened from the east on 9 May and a scaffolding collapsed in strong winds injuring two persons in the evening.

    Rain eased off late on 10 May and winds turned southerly the next day and the weather became fine with long sunny periods. Temperatures increased progressively the next few days, reaching a maximum of 31.8 degrees on 16 May, the highest of the month. Late in that evening, squally thunderstorms and heavy showers associated with a trough of low pressure swept across Hong Kong. The weather remained showery and thundery for the next few days as the trough lingered around the coastal area.

    Easterly winds strengthened again on 21 May and subsided late next day. The weather remained generally cloudy apart from some isolated heavy showers over Hong Kong Island on the morning of 22 May. The minimum temperature of 21.3 degrees recorded on 24 May was the lowest temperature in the month.

    Under the influence of a drier airstream, it became fine with long sunny periods on 25 May and fine weather prevailed until 28 May. A trough of low pressure over south China moved southwards bringing cloudy weather on 29 May and some showers the next day. As the trough dissipated, fine and sunny weather returned on the last day of the month.

    Three tropical cyclones occurred in the western North Pacific and the South China Sea in the month.

    During the month, a total of seven aircraft was diverted due to adverse weather.