HEAT Hazard Postcode Data FAQs

4EI is providing Heat Hazard Postcode Data under a free license to organizations that need to respond to Covid19 and protect vulnerable populations from the effect of heat stress during lock down. This is supported through the Ordnance Survey Covid19 response license. Below are the frequently asked questions we have collated for you.

1. How do I use this data?


4EI: A Heat Hazard score ranging from 1 to 5 is provided for every postcode in Great Britain (5 referring to high heat hazard risk, 1 referring to low heat hazard risk). Each postcode can be queried to understand the likelihood that a significant heat event (i.e. a heat wave) will have a high impact. This can help to inform several things:


  • Identification of ‘hot spot’ locations to target medical resources to hospitals which are likely to have an admission increase during heat waves;

  • Understand which parts of the population are most at risk when a heat wave occurs;

  • Understand where to plan and focus heat wave mitigation strategies (e.g. informing the population that they are at risk, and measures they can take to mitigate the risk);

  • Support the creation of business continuity plans and corporate mitigation strategies, targeting of cooling products, identification of heat refuges and infrastructure protection;

  • Support compliance with planning policies (e.g. understand which locations may be impacted by heat effects and where new developments may increase the local heat effect).


During a hot weather event, government guidelines should be followed to mitigate the effects on health and wellbeing. The definition of a heat wave, and recommended mitigation activities can be found at the following web pages:




2. What was the source data for this product?


4EI: The Heat Hazard data is derived from satellite data. The satellite used was LandSat 8 (operated in collaboration between by NASA and USGS). LandSat 8 satellite has been operating since 2013, capturing images of the entire Earth every 16 days, creating a large archive of information. The satellite has a Thermal Infrared Sensor, with archive data being processed by 4 Earth Intelligence, to understand Land Surface Temperature. 

3. How was the heat hazard product created?


4EI: The Heat Hazard Data set has been created using archive satellite data from Summer months during 2017, 2018 and 2019 across all of Great Britain. Several satellite images were processed each year to produce several Land Surface Temperature values for each location in Great Britain. The data was then combined and statistically analysed to produce an average heat risk value for every 30 metre square. Finally values were amalgamated, to provide an average heat risk value for each postcode.

4. What's the accuracy of the heat hazard value?


4EI: Satellite raw data outputs have an inherent temperature uncertainty range of approximately +/- 4C, when compared to air temperature values. This uncertainty is mitigated during data processing using conventional calibration methods. Uncertainty is further removed as multiple satellite images have been combined to create the Heat Hazard value. As the heat data is created from several images, and we are not reporting heat values, the data can be used as an indication of where areas are consistently hotter and are therefore likely to suffer greater heat stress than other areas.


The provision of a heat hazard value is a “relative” indication of heat risk for every postcode in Great Britain, when compared to other postcodes.


5. What's the spatial accuracy / resolution?


4EI: The processed satellite data allows a Land Surface Temperature (LST) output at a resolution of 30m (in other words a Land Surface Temperature value for every 30m sq). LST values are then amalgamated to provide a value for every postcode.


The satellite data has an inherent accuracy of 12 meters circular error, with 90-percent confidence.


6. What does the data show?


4EI: The Hazard Category 1 to 5 is provided for every postcode in Great Britain (5 referring to high heat hazard risk, 1 referring to low heat hazard risk). 


You can use these classes to show “High”, “Medium” and “Low” heat hazard locations on map bases if you have an internal geographical information system.  


The data can also be combined with other datasets or spreadsheets you hold if they also have postcode information e.g. if you hold information on vulnerable populations or postcodes that are looked after by volunteers or responders.

7. Why is there a high hazard score in some rural areas?


4EI: During hot and dry conditions, evidence has been seen of high albedo from soil, which has a warming effect on the land.

8. Can I use the map alongside other geographic data such as OS mapping / address point / UPRN?


4EI: The data is provided as a hazard value for every postcode in Great Britain. Providing the data by postcodes means that the data can easily be used alongside a wide range of other data sets. 


9. Is anyone using this data?


 4EI: 4 Earth Intelligence have provided Bristol City Council with Land Surface Temperature data to inform their urban heat resilience planning. The data is being combined with other GIS layers to provide insights into heat vulnerability and the location of hotspots. This will help the Council identify where interventions are needed through urban spatial planning, the built environment, public health or emergency planning to reduce heat-health risks.


10. Is the data GIS compatible?


4EI: The data is provided in .CSV format, and can therefore be easily ingested into all industry standard GIS systems. 

11. Does the Heat Hazard Map already show what areas of the country will be most affected by a heatwave, and what areas are those?

4EI: yes, as one would expect it's in urban areas, but the impact can vary within the urban landscape. Areas with blue and green infrastructure are typically less affected (close to parks, lakes and watercourses), as they benefit from a natural cooling effect when compares to man-made infrastructure.

12. Would this also be useful to insurance companies who want to identify prime real estate areas?

4EI: Yes, if they want to look at Carbon zero (air conditioning increases energy use) and property desirability. It's also of interest to developers to understand what measures they need to apply in terms of ventilation, and planners to asses what policies should be applied and what sites should be approved.

13. What are the automated algorithms providing along with the satellite imagery from the past three years?


4EI: Those are algorithms developed by 4EI using the best available earth observation scientific knowledge.

14. How do you expect agencies to be able to use the postcode data from the Heat Hazard Map tp save lives? 

4EI: They will be essentially using complex EO science distilled to a simple and useable form for the end-user. The data is converted into a spreadsheet, separated by postcodes data making it much easier to understand and use. They can quickly understand where there are potential impact areas and can use low tech approaches such as letter drops and door to door notification if appropriate. They can also match that data to their own vulnerable population datasets by using the postcode field for very targeted approaches.

15. How much difference in temperature is anticipated between the 2017-2019 data and 2020?

4EI: We are only reporting actual events, not predictive at this stage but we are investigating forecasting for future editions.

16. What are the five categories the heat anomalies were broken into to show the higher temperatures in different locations?

4EI: Satellite data has been statistically analyzed to rank each location on a scale of 1 to 5, with 1 showing previous heat events of having a low impact, and 5 showing previous heat events of having a high impact on surface temperature vs the surrounding area. 

17. The FAQs don’t cover my query - what can I do?

4EI: For any additional questions regarding the Heat Hazard Data, please contact heat@4EI.co.uk.


The data was derived from satellite imagery captured over the summers of 2017 to 2019. Automated algorithms were used to produce information on land surface temperature. Further processing allowed the data to be standardised across different locations, and then was statistically analysed to show the location of heat anomalies throughout Great Britain. Heat anomalies were then split into five categories, demonstrating the tendency of different locations to reach higher temperatures.

Contact us on heat@4ei.co.uk for more details or if you would like to access the higher resolution data.


An understanding of heat impact form space enables emergency responders to target those most vulnerable to heat stress during the Covid19 pandemic through low tech solutions such as letter drops or door to door communications.