Ocean Heat Dome Steams Coastal China: Shanghai to Near Very Dangerous 35 Degree Celsius Wet Bulb Temperatures This Week

Shanghai Under Ocean Heat Dome

Shanghai, southeast China swelter under Ocean Heat Dome.

(Image source: NASA/Lance-Modis)

An ocean heat dome that formed over a broad area of the Pacific Ocean, the South and East China seas, and a large stretch of coastal China during late July continues to create a dangerous combination of record hot temperatures and high humidity.

According to reports from AccuWeather, the sweltering coastal China town of Shanghai hit a new all-time record high temperature of 105.8 degrees Fahrenheit (41 degrees C) on Tuesday. But this marker may just be a milepost to what is predicted to be a 107-108 degree scorcher on Wednesday and Friday. With humidity predicted to be around 50% and barometric pressure readings expected to hit 1005 millibars, these represent extraordinarily dangerous conditions.

The human wet bulb limit: 35 C

Recent climate papers by former NASA scientist James Hansen have issued warnings of the potential for wet bulb temperatures on the surface of the Earth to start to exceed levels that are lethal for humans at 35 degrees C  for longer and longer periods as humans continue to warm the atmosphere. Hansen notes:

One implication is that if we should “succeed” in digging up and burning all fossil fuels, some parts of the planet would become literally uninhabitable, with some time in the year having wet bulb temperature exceeding 35°C. At such temperatures, for reasons of physiology and physics, humans cannot survive, because even under ideal conditions of rest and ventilation, it is physically impossible for the environment to carry away the 100 W of metabolic heat that a human body gene rates when it is at rest.

Different from direct air temperature, wet bulb readings measure what air feels like on the surface of the skin. The measure simulates the cooling effect caused by human sweat evaporating from the skin surface. In very dry, hot conditions, human skin temperature can remain below this lethal level as the rate of evaporation increases due to dryness. Since most of the world’s hottest regions are very dry, humans can withstand air temperatures of 120 degrees (Fahrenheit) and above. Thankfully, it is very rare that extraordinarily hot and humid conditions occur in the same locations. This is generally due to a cooling affect provided by an adjacent ocean mass — as most damp regions are also near or surrounded by cooler ocean air.

The Ocean Heat Dome

Enter the weather conditions forecast for Shanghai tomorrow and Friday…

A massive heat dome high pressure system has settled, not just over land areas of China, but directly over a large region of the Pacific Ocean and adjacent China seas. The result is that sea surface temperatures are now ranging 1-4 degrees Celsius above the already warm 1971-2000 average with a large area showing temperatures above 30 degrees Celsius (86 Fahrenheit). This large region of hot water and corresponding hot ocean air is pumping both heat and humidity into the Shanghai region. Hot ocean air is being pumped over Southeast Asia where it mixes with the already baking land mass air to form a brutal brew of very high heat and high humidity. The clockwise flow of the heat dome then pulls this mixture of record hot and humid air over the highly populated regions of Shanghai.

These ocean-based heat dome conditions are not normal, with typical heat dome conditions usually forming over land. The danger in this particular set of conditions is that very high heat combines with higher than usual humidity to result in much greater heat injury risks for humans.

Ocean heat dome

Sea surface temperatures under Ocean Heat Dome

(Image source: Weather Online)

Forecasts for tomorrow and Friday are showing Shanghai temperatures will probably reach at least 107-108 degrees Fahrenheit (42 C) in an area where relative humidity is forecast to be 50% and where barometric pressures are forecast to remain around 1005 millibars of mercury. This brings us to the extraordinarily dangerous high wet bulb temperature of 33 degrees Celsius.

Please do your best to stay safe

In such instances, the best defense is to find a cool, shaded location and limit exposure to heat during the hottest times of the day. Drinking cold fluids can also aid in reducing core body temperatures. A common heat mitigation aid is freezing a bottle of water and carrying it in a pocket next to your thigh. The cold bottle will contact the skin near the femoral artery, cooling blood there and transporting this cooler blood throughout the body. If extreme heat is still too much, placing the bottle in direct contact with the large veins in the neck will provide even more efficient cooling. This simple cooling pack also doubles as a means to replenish vital fluids.

Under such conditions, it is also important to be alert for signs of heat exhaustion and heat stroke to include:

  • Confusion
  • Dark-colored urine (a sign of dehydration)
  • Dizziness
  • Profuse sweating
  • Weakness
  • Muscle cramps
  • A lack of sweating

China has also activated emergency operations facilities and is providing information and aid in the hardest hit regions.

Unfortunately, record heat is expected to continue over Shanghai through at least next Wednesday with only one day expected to see below 100 degree (F) readings. With so many already dealing with heat stress, our best hopes are that all there will have the means to remain safe.

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Colorado Bob


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Leave a comment


  1. Meanwhile in Pakistan and Afghanistan monsoon floods kill dozens (from 4th Aug 2013)


  2. As someone who grew up in a hot and humid climate I know a little about how to keep cool. I always found it helpful to stick my head under a tap and let the water completely saturate my hair and head. I would repeat this each time my hair had dried naturally and without using any towels. The human head produces a lot of heat and keeping your head wet and cool helps to keep body temperature comfortable.


  3. Steve

     /  August 6, 2013

    Isn’t the monthly sea ice level report in by now? Maybe they are having a hard time calculating how much ice is left with all the smoke in the air. 🙂


  4. Yep.


  5. Steve

     /  August 6, 2013

    The weather shouldn’t be as entertaining as playoff football, but at the increased rate that events are occuring at, it’s moving in that direction quickly!


  6. Hey Robert,

    This may be off the topic, but you might be interested in reading this.



  7. A bus is seen on fire on a street in Beijing. The fire might have been due to high temperatures and no casualties have been reported, local media said http://www.telegraph.co.uk/earth/earthpicturegalleries/7874578/Chinese-heatwave-in-pictures-record-summer-temperatures-in-parts-of-China.html?image=5


  8. Steve

     /  August 7, 2013

    The media as a whole at times is unbelievable. One of those times is with this heat wave in China right now. There are few, if any new stories, talking about this unrelenting heat wave. However, every media outlet seems to have covered the one story about a guy pretending to have been killed by the government, but springing to life after being under a sheet for two hours on the street because the heat was unbearable. I can’t imagine that people aren’t dying by the thousands there. I think they aren’t fully disclosing the severity of the problem. Thoughts?


  9. Steve

     /  August 7, 2013

    This was the best I could find about it http://news.xinhuanet.com/english/china/2013-08/06/c_132607372.htm. Maybe they can deal with the heat a lot better than Russia and Europe. But those two heat waves left like 90,000 dead as reported in that clip that was attached in a post from a program in Australia a week or so ago about climate change. I’m curious whether they are that much better conditioned to deal with the heat or if their government is once again acting trying to downplay the severity of the event due to concern of rebellion.


  10. Bryan

     /  August 7, 2013

    Have long suspected the rapid state switch to global warming, everyone talks about what the climate will be like in 50 or 100 years but that isn’t how it’s going to work. It’ll have gone all to hell long before then. Especially for us humans. And you can forget the economy.
    I’m surprised there’s no mention of water immersion as a body temp alleviation method. Drink all the water you want and rub all the ice on your thigh you can, will never work as well as a bath. Water circulates heat far better than air and will just keep taking it from you.
    Keep putting your head under as well.


    • Just to note —

      If you are suffering from heat stroke or heat exhaustion, water immersion can kill due to shock. But immersion as mitigation is a good technique if you have the water readily available.

      As for the doomerism… a little bit goes a long way.


  11. Loni

     /  June 24, 2015

    Thank you for the post Robert. All of this heat, and it’s still June………it’s gonna be a hot summer if this is any indication.

    I hope the Arctic can hang on to those clathrates.


    • This was an earlier report during the summer of 2013. I linked it as it was a reference to hitting wet bulb temperatures that are lethal to human beings.


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