EXTREMA Heat Alert Mobile Application

Solution Overview

Paris launched the EXTREMA mobile application in late June 2018 to provide residents and visitors with real-time information about cooling locations during extreme heat events.[1][2] This technology-enabled approach combines satellite data, thermal mapping, and an interactive digital platform to help vulnerable populations navigate the city's network of cool islands during dangerous heatwaves.[3][4] The initiative emerged following the devastating 2003 heatwave that caused approximately 500 deaths in Paris and 15,000 across France, prompting municipal authorities to develop comprehensive heat adaptation strategies.[5][6]

Technical Components

The EXTREMA system uses real-time satellite data combined with model-based and city-specific information to estimate temperature, humidity, and discomfort index for every square kilometer across Paris.[7][8] Temperature estimates are updated every five minutes, providing spatial and temporal resolution unavailable from other services.[9][10] Between 2014 and 2016, the City of Paris conducted foundational research on the thermal regulating effect of green and humid spaces, combining field measurements in green spaces and nearby urban areas with aerial thermography maps.[11] The mobile application evaluates personalized health risk for users at their current location, and when risk levels are high, the system alerts users and provides recommendations with routing instructions to the nearest cooling centers.[12] The platform provides information about diverse cool spots including air-conditioned rooms, parks, shady streets, fountains, and water availability locations such as public taps, springs, and animal watering holes.[13] The application was provided in four languages at launch, making it particularly useful for foreign visitors.[14]

Implementation Details

The City of Paris developed EXTREMA in collaboration with the Agence Parisienne du Climat, EIVP (École des Ingénieurs de la Ville de Paris), and APUR (Atelier parisien d'urbanisme).[15] The application was also developed in partnership with France's public health authority and weather agency Météo France.[16] In the context of the climate adaptation strategy (2015) and the new Paris Climate Plan (2018), the City asked Apur to define, locate, and map cool air itineraries and islands throughout Paris.[17] The project was implemented in 2018-2019, with the full suite of EXTREMA services released in summer 2018.[18][19] Initial investments totaled $852,564 since 2018.[20] More than 800 cool islands were identified in 2018 as accessible during the day and 150 at night, with the network composed of spaces ranging from parks and forests to swimming pools and museums.[21][22] Multiple users downloaded and evaluated the mobile app, making EXTREMA Paris the most downloaded app of the city during its launch week.[23] In 2022, the option for cool routes was added where users can choose the coolest route to reach their destination.[24]

Benefits and Impacts

During the first year of use in 2018, the EXTREMA app was downloaded 6,000 times.[25] The application lists around 800 to 1,000 different places suitable for those seeking refuge from high temperatures.[26][27] Users can create profiles for friends or family members to check if their loved ones are safe during a heatwave, with the system monitoring whether users or family members might be in critical situations.[28][29] The City of Paris places an interactive map on its website annually so users can identify the best places to escape the heat.[30] Cool air itineraries are available to the general public through dynamic maps on the paris.fr site, with separate maps for daytime and nighttime access.[31] More than 7,000 Parisians have been identified as vulnerable during times of extreme heat, and the EXTREMA project aims to inform those residents of heat risks and how and where to cool off.[32] The city has added 62 hectares of green space and 4.7 hectares of green roofs to alleviate the urban heat island effect.[33] By 2020, Paris aimed to ensure all Parisians would be within a seven-minute walk of a cool island.[34] By 2030, the City plans to create or open to the public at least 300 additional cool islands and routes.[35] Social benefits include strong public support, with 80% of Parisians supporting initiatives to create more green spaces in the city.[36]

Climate Adaptation Relevance

The EXTREMA system directly addresses extreme heat events, which pose severe consequences for Paris, particularly for elderly residents and those in ill health.[37] The application proposes an innovative approach that exploits high smartphone penetration in Europe through a mobile application for the public and an administration web hub for local authorities to improve resilience to extreme temperature events.[38] The initiative aims to prevent disasters like the 2003 heatwave from becoming more common as climate change intensifies urban heat island effects.[39]

Business Analysis

Green party councillor Célia Blauel noted that Paris and Athens were the first cities to launch such a cooling app, though Rotterdam also deployed a version of Extrema.[40] The project received initial investments of $852,564 since 2018, supporting the development and deployment of the mobile application and associated infrastructure.[41] By 2020, Paris planned to build 100 additional hectares of green roofs, one-third of which would be used to produce fruit and vegetables, representing an integrated approach to climate adaptation and urban agriculture.[42] The strong public support for green space initiatives, with 80% of Parisians backing such measures, suggests favorable conditions for continued investment in heat mitigation infrastructure.[43] The multi-agency partnership model involving municipal authorities, public health agencies, meteorological services, and urban planning organizations demonstrates a collaborative governance approach to climate adaptation financing and implementation.[44]

Fact Base

[1]: EXTREMA launched in Paris June 29, 2018 Following Rotterdam and Athens, EXTREMA mobile app launched at the city of Paris in the end of June. [2]: In 2018, this data will be used to develop a mobile application with real-time information about the closest cool areas, and the coolest routes to take. [3]: EXTREMA (project using real-time satellite data, along with other model and city-specific data to estimate the temperature, humidity, and discomfort index for every square kilometre in the city). [4]: The network of cool islands is composed by more than 800 spaces, from parks and forests to swimming pools and museums, where residents and visitors can take a break from the city's summer heat. [5]: Around 15,000 old people died across France, including 500 in Paris, from the effects of that heatwave. [6]: The heat wave of 2003 caused several deaths among elderly Parisians. [7]: EXTREMA uses real-time satellite data, along with other model and city-specific data to estimate the temperature, humidity, and discomfort index for every square kilometer in the city. [8]: EXTREMA uses real-time satellite data, along with other model and city-specific data to estimate the temperature, humidity, and discomfort index for every square kilometer in the city. [9]: Temperature estimates are updated every 5 minutes, providing data at a spatial and temporal resolution that is not available from any other service. [10]: The app can tell you, thanks to data that is updated every five minutes, if your grandmother might be in a critical situation, and it can tell you what you need to do [11]: Between 2014 and 2016, the City of Paris conducted a study on the thermal regulating effect of green and humid spaces in the Paris area. This study combined field measurements in green spaces and nearby urban areas with aerial thermography maps. [12]: The mobile app evaluates the real-time personalised health risk of the user at his/her location, and if high, it alerts him/her and provides recommendations and routing instructions to the nearest cooling centres. [13]: The user enters the application environment and by entering information such as their location they can retrieve useful information such as where the cool spots around them are (air-conditioned rooms, parks, shady streets, fountains and more) and where there is water availability (e.g. public taps, springs, animal watering holes, etc.). [14]: The application is already provided in 4 languages making it particularly useful for foreign visitors as well. [15]: The city of Paris, together with the Agence Parisienne du Climat, the EIVP (École des Ingénieurs de la Ville de Paris) and the APUR (Atelier parisien d'urbanisme) and EXTREMA. [16]: One of the aims of the app, which was developed in collaboration with France's public health authority and weather agency Météo France [17]: In the context of the strategy of adapting to climate change (2015) and of the new Paris Climate Plan (2018), the City of Paris asked Apur to define, locate and then make a map of the cool air itineraries and islands in Paris. [18]: The project was implemented in 2018-2019. [19]: In summer 2018 EXTREMA full suite of services will be released. [20]: Since 2018 Initial Investments 852,564 USD [21]: More than 800 cool islands have been identified in 2018 as accessible during the day and 150 at night. [22]: The network of cool islands is composed by more than 800 spaces, from parks and forests to swimming pools and museums, where residents and visitors can take a break from the city's summer heat. [23]: Multiple users downloaded and evaluated the mobile app making EXTREMA Paris the most downloaded app of the city that week! [24]: Also, in 2022, the option for cool routes was added where the user can choose the coolest route to their reach its destination. [25]: This practice seems to be quite successful as an indicator during the first year of use of the app (2018), EXTREMA has been downloaded 6,000 times. [26]: Around 800 different places are listed on the app as being suitable for those seeking to take refuge from high temperatures. [27]: Around 1000 different places that are suitable for those who seek for a refuge from high temperatures, are listed in the app. [28]: Users of the app can create a profile and find the places nearest to them. And they can also create a profile for friends or family so that they can check to see if their loved ones are safe during a heatwave. [29]: The app can tell you, thanks to data that is updated every five minutes, if your grandmother might be in a critical situation, and it can tell you what you need to do [30]: The City of Paris will place an interactive map on its website every year so that users can identify the best places to escape the heat. [31]: Cool air itineraries are available to the general public in the form of dynamic maps on the paris.fr site where you can find a map of the daytime and one for the night time. [32]: More than 7,000 Parisians have been identified as vulnerable during times of extreme heat, and this project aims to inform those residents of heat risks, and how and where to cool off. [33]: The city has already added 62 hectares of green space and 4.7 hectares of green roofs. [34]: By 2020, the goal is for all Parisians to be within a seven-minute walk of a cool island. [35]: By 2030, the City will create or open to the public at least 300 cool islands and routes. [36]: Social Benefits – 80% of Parisians support the initiatives to create more green spaces in the city, which will lead to a more pleasant living environment [37]: In Paris, a natural disaster such a severe heat wave could have serious consequences. The heat wave of 2003 caused several deaths among elderly Parisians. [38]: EXTREMA proposes a new innovative and effective approach that aims to exploit the high penetration of smartphones in Europe in the form of a mobile application for the public, and an administration web hub for the local authorities. [39]: Health Benefits – Fifteen thousand people died in France during a heat wave in 2003. To prevent such disasters from becoming more common, Paris is protecting its citizens – particularly the elderly and those in ill health – from excessive heat. [40]: With (the Greek capital) Athens, we are the first to launch such an app, said green party councillor Célia Blauel, who appeared to have overlooked the fact that the Dutch city of Rotterdam also has a version of Extrema. [41]: Since 2018 Initial Investments 852,564 USD [42]: Going forward, vegetation must be planted on all new buildings, and, by 2020, the city will build 100 additional hectares of green roofs – one-third of which will be used to produce fruit and vegetables. [43]: Social Benefits – 80% of Parisians support the initiatives to create more green spaces in the city, which will lead to a more pleasant living environment [44]: The city of Paris, together with the Agence Parisienne du Climat, the EIVP (École des Ingénieurs de la Ville de Paris) and the APUR (Atelier parisien d'urbanisme) and EXTREMA.