Hong Kong Heat Index

In the UK, wind chill is a term heard frequently. It’s when the temperature feels a lot colder than it actually is due to the air flow around us. Not only does it feel colder but it has the same effects of actually being colder than the stated temperature. The last time I was working in the UK it was 5 degrees with a wind chill factor of -12, so it was actually -7 degrees on my skin.

In Hong Kong, we have the heat index which is the opposite of wind chill. Heat Index combines air temperature and relative humidity. And because the humidity in Hong Kong can often be in the high 90’s, the heat index can often add up to 15 degrees to the actual temperature recorded by the Hong Kong Observatory.

Below is a chart showing the Heat Index and associated temperature that you will feel given the current humidity level in the shade. If it’s 33 degrees in Hong Kong and the relative humidity is 85%, then the temperature that you feel will actually be 50 degrees Celsius.  At 50 degrees, heat exhaustion is likely. It is highly important therefore that we are familiar with our surroundings.

Heat Index

Heat Index temperature readings for Hong Kong in the shade.

Above 30C – Extreme Caution: Heat cramp and exhaustion possible
Above 40C – Danger: Heat exhaustion likely
Above 55C – Extreme Danger: Heat stroke imminent

Another important factor is sunlight. In addition to the above heat index, if you are standing in direct sunlight, you must add another 8 degrees. So with the above example of 33 degrees and 85% humidity plus 8 degrees for direct sunlight, you are destined for heat stroke!!

As a result of Hong Kong’s extreme weather, we have added live weather information, which you can find at the bottom of each and every page of our website. Before going out for a hike be sure to check it, and if both temperature and humidity are high, and if you are likely to be hiking in direct sunlight, make sure of the following:

Hiking Above 30 Degrees

  • Take plenty of water. 1 litre of water for every 1 hour of hiking.

Hiking Above 40 Degrees

  • Substitute water for an electrolyte-rich sports drink. 1 litre of sports drink for every 1 hour of hiking.
  • Wear lightweight, light-colored, loose-fitting clothing and a cap.
  • Use a sunscreen with a sun protection factor (SPF) of 15 or more.

Hiking Above 55 Degrees

  • Stay home.

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