Hong Kong Observatory Open Data API

What you can build

• Release staff on a tropical cyclone signal

  warnsum reports WTCSGNL with the signal code in force. When the code reaches the level in your policy, the operator proposes the release notice and the roster change, and records who approved it.

  With Severe Weather Notice, Event Surge

• Hold local deliveries under a Black Rainstorm

  WRAIN carries subtype WRAINA, WRAINR or WRAINB. On WRAINB the operator proposes holding every order due out that hour and releases the hold once the summary no longer lists it.

  With Weather Hold

• Reset the shuttle timetable when rain sets in

  hourlyRainfall.php gives the past hour by station every 15 minutes. Above your threshold at the stations near a property, the operator proposes extra runs and posts the change on your approval.

  With Shuttle Timing

• Prepare buildings before a storm arrives

  fnd shows the 9-day outlook and flw carries tcInfo. When a tropical cyclone appears in either, the operator proposes the pre-storm checklist for each building and logs its completion.

  With Storm Prep

Requirements

• The dataType code per dataset (flw, fnd, rhrread, warnsum, warningInfo, swt) and lang set to en, tc or sc
• Station codes such as HKO, HKA or CCH, and a year, for the climate series on opendata.php
• Attribution to the Government, the Hong Kong Observatory and DATA.GOV.HK under the DATA.GOV.HK Terms and Conditions
• Parsers that tolerate absent fields, since a parameter is omitted when its value is null

Authentication

None. Every endpoint under data.weather.gov.hk/weatherAPI/opendata is an unauthenticated HTTP GET with dataType and lang query parameters.

Limits

• No push channel; warnings and tips update as and when there is a change, so you poll weather.php
• Hourly station rainfall is provisional with limited validation and differs from the Observatory's climatological record
• Response shapes vary: null parameters are dropped, hourly rainfall returns M under maintenance, and uvindex is an empty string when absent
• opendata.php returns CSV unless rformat=json; tide and sun tables cover a fixed span of years

Questions and answers

How do I read the tropical cyclone signal?

Call weather.php?dataType=warnsum&lang=en. When a signal is in force the response has a WTCSGNL property whose code names the signal, such as TC1 or TC3, with name and updateTime. warningInfo returns the full statement contents. Both change as and when there is an update, so poll.

Is there a key or a rate limit?

No key. The API documentation names no rate limit and no registration; the data is published under the DATA.GOV.HK Terms and Conditions, which allow commercial and non-commercial use with attribution to the Government, the Hong Kong Observatory and DATA.GOV.HK.

Which formats and languages are returned?

weather.php, earthquake.php and hourlyRainfall.php return JSON. opendata.php returns CSV by default and JSON with rformat=json, as a fields list plus data rows. lang accepts en, tc and sc; the default is en. Times use the +08:00 offset.