Heat Wave


Heatwaves – do we get them in the UK? Well, we certainly had one in the summer of 2022, even if it was only for a few days. However, how many summers have we sat in house looking out at the rain wishing we could have that heat wave right now! The reality is what we really want is temperatures in the mid 20’s, which allow us to walk around in flip flops and T-shirts but carry on our daily activities. 

Interesting fact

The hottest month on record was July 2021 according to the National Oceanic and Atmospheric Administration.

Local Risk Rating

Heat Wave is assessed as Very High risk on our Community Risk Register. Take a look at the table shown in What is Risk? to understand why.

  • Impact: Significant (4)
  • Likelihood: Medium (3)
  • Rating: Very High

What is it?

A heatwave is an extended period of hot weather, relative to the usual expected temperatures in that area for that time of year. So that means what’s classed as a heatwave in the UK is different to what is classed as a heat wave in other countries. For example, Norway’s heatwave definition states it must be over 28 degrees for 5 days, which is unlikely to be classed as a heatwave in the UK.

In the UK, a heatwave is declared when temperatures meet a set threshold for 3 or more consecutive days. What makes it more complicated is the fact that different counties have different thresholds. Wiltshire’s heatwave threshold is 27 °C, Cambridgeshire’s is 28°C and East Riding of Yorkshire is 26°C. So not much difference but the point is they are different. 

These thresholds are calculated by the Met Office using climatology of daily maximum temperatures at the mid-point of summer (15th July). These thresholds have risen over the years as temperature generally rise around the globe.

Heatwaves are most common in the summer months when high pressure develops over an area. These systems are slow moving and can stay in place for several days or weeks.

What are the effects?

There are many serious effects of a heatwave that includes:

  • Vulnerable members of the public struggling to keep cool and becoming seriously ill
  • Widespread wildfires
  • ‘Melting’ of roads
  • Buckling railway lines
  • Droughts (potentially further down the line)
  • Shut down of industries (unable to work in the heat)
  • Dehydration and sunburn

Of course, there are also the less serious impacts like the inability to buy ice cream as everyone has got there before you and the difficulty in sleeping at night!


Summer 2022 was a time of extreme heat for many in China. Temperatures of above 40°C were seen for nearly 2 months which broke many local records. It led to widespread impacts on the country which included:

  • River and reservoir levels drastically falling (disrupting hydroelectricity generation)
  • Factories shut down (lack of electricity, much of which is going to domestic air conditioning)
  • Electricity shortages
  • Huge areas of crop damage (lack of rain)

The extreme heat in China meant that subways were set up as rest areas where people could shelter and recover from the heat.

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What are we doing about it in the LRF?

The LRF has assessed heatwaves as a very high risk which means that we carry out in-depth work to plan and prepare for them. We have national and local heatwave plans that are regularly updated and ‘practised’. The Met Office also monitors heatwaves and provides advice and mapping to help areas monitor the ongoing situation.

Many of the effects of heatwaves are mitigated against or responded to by individual agencies all of which will come together to share information, situational awareness and plans. For example, a wildfire will affect the surrounding community. It will not only impact on the Fire and Rescue Service, who will primarily fight the fire but other agencies will also have a role to play such as the Local Authority whose public health department will monitor air quality.  The NHS could be impacted with an increase in patients reporting respiratory problems.

What can you do?

What we ask you to do in a heatwave is generally centred around looking after yourself. Remembering to cover up in the sun, limit the time outside (in particular in the middle of the day), drink plenty of water to remain hydrated and make sure your family and friends are supported throughout.

Many people will point to the fact that other countries have this heat all the time, the difference here is that we aren’t used to it. Many of us don’t have aircon or swimming pools; we also try to carry out our normal activities despite the heat! Remember to consider the situation you are in, it’s probably not the best idea to paint the fence in a heatwave – save that for the days where its much cooler!


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Heatwave Risk

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