Extreme Heat Data Pathfinder

Extreme heat events lasting a few days to weeks at a time are occurring more frequently in major cities across the world and can have detrimental impacts on public health. NASA data can help forecast and monitor these events.
Information on extreme heat events. Click on image for larger view. Credit: U.S. Centers for Disease Control and Prevention (CDC).

Heat waves are occurring more frequently in major cities across the nation, and are periods of abnormally hot weather (which may be accompanied by abnormally high humidity) lasting a few days to a few weeks. In the 1960s, major cities in the U.S. averaged about two heat waves per year. In the 2010s, that number rose to more than six heat waves per year. Even under different climate models and emission scenarios, results indicate that extreme heat events are becoming worse.

This Data Pathfinder is designed to help guide you through the process of selecting and using datasets applicable to extreme heat, with guidance on resolutions and direct links to the data sources. If you are new to remote sensing, the What is Remote Sensing? Backgrounder provides a good overview. In addition, NASA's Applied Remote Sensing Training Program (ARSET) provides numerous training modules, including Fundamentals of Remote Sensing.

If you have specific questions about how to use data, tools, or resources mentioned in this Data Pathfinder, please visit the Earthdata Forum. Here, you can interact with other data users and NASA subject matter experts on a variety of Earth science research and applications topics.

An Overview of Extreme Heat

The public health impacts of heat waves include exhaustion or heat stroke, and even death. Extreme heat results in about 600 deaths per year in the U.S., with the elderly, very young, outdoor workers, and people with mental illness and chronic diseases at higher risk.

In monitoring heat waves, it's important to use long-term data records to assess abnormalities from normal conditions. These robust, sustainable, and scientifically sound records of temperature, humidity, and other environmental metrics, collected over decades, form a climate data record that can be used to reliably assess climate change. For example, NASA's Terra satellite has been acquiring land surface temperature data since 2000 and NASA's Aqua satellite has collected similar data since 2002. With consistent and continuous data coverage, reliable temperature and humidity anomalies can be assessed.

Urban heat islands play an important role in extreme heat events. Cities tend to have higher temperatures than outlying, more rural areas. This is due to the differences in radiative and thermal properties of varying surfaces, especially impervious surfaces such as buildings, pavement, and roads as well as the spatial distribution of water, soil, vegetation, and human-created surfaces.

Find the Data

Air and land surface temperature data are useful for assessing changes in weather and climate patterns.
High humidity is a key element in determining the heat index for an area. NASA provides remote sensing and modeled measurements of relative humidity.
Changes in land cover derived from satellite imagery and socioeconomic data can be used to assess the growth and impact of urban heat islands.
Weather maps produced from model data and satellite observations can be used to create medium and long-range forecasts of temperature, humidity, wind speed, and precipitation.
Heat-related deaths are preventable, but prevention requires a knowledge of where vulnerable populations exist and the interventions needed in these communities.
Use the Data

The following use cases show some of the many ways Earth observation data support research and management of extreme heat:

Connection of Sustainable Development Goals to Extreme Heat

The Sustainable Development Goals (SDGs) are a collection of 17 interlinked global goals designed to be a blueprint for a sustainable future for all of Earth’s inhabitants. The SDGs are part of the 2030 Agenda for Sustainable Development, an international plan signed by all United Nations (UN) member states in 2015 and underpinned by the foundational components of People, Planet, and Prosperity. The 17 SDGs in the Agenda are made up of 169 objectives that include specific social, economic, and environmental targets. These targets provide a blueprint for developing a more sustainable global future.

Data acquired remotely by sensors aboard satellites and aircraft or installed on the ground play a unique role in tracking the progress toward achieving the SDGs. These remotely sensed Earth observations provide consistent and continuous information on the state of Earth processes and their change over time. These data also are integral components of socioeconomic metrics that provide a measure of how humans co-exist with the environment and the stresses they encounter through natural and human-caused changes to the environment.

NASA Earth observation data are available without restriction to all data users, a policy that is being adopted by other international space agencies and one that reduces the cost of monitoring the SDGs and provides developing countries a means to acquire and utilize these data for other policy-making purposes.

NASA’s datasets are organized by topics that help users to locate, access, and apply relevant and complementary datasets for each SDG. The Extreme Heat Data Pathfinder addresses (but is not limited to) the following SDGs:

SDG SDG Goals Relevant to Health and Air Quality
Goal 2. End hunger, achieve food security and improved nutrition and promote sustainable agriculture 
  • Target 2.4: By 2030, ensure sustainable food production systems and implement resilient agricultural practices that increase productivity and production; that help maintain ecosystems; that strengthen capacity for adaptation to climate change, extreme weather, drought, flooding, and other disasters; and that progressively improve land and soil quality

Goal 13. Take urgent action to combat climate change and its impacts

  • Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters in all countries

Goal 15. Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss

Target 15.3: Combat desertification, restore degraded land and soil, including land affected by desertification, drought, and floods, and strive to achieve a land degradation-neutral world

The opportunities to connect NASA data to the SDGs are infinite; therefore, the datasets included in specific Data Pathfinders are not intended to be comprehensive. Additionally, NASA datasets are not official indicators for SDG monitoring and decision-making but are complementary.

Tools for Data Access and Visualization

Earthdata Search | Panoply | Giovanni | Worldview | AppEEARS | MODIS/VIIRS Subsetting Tools Suite

This section provides links to tools and applications relevant to analyzing and visualizing heat-related data referenced in this Data Pathfinder. NASA's Earth Science Data Systems (ESDS) Program maintains many more resources for data analysis that may be helpful. Explore the full list on the NASA Earthdata Data Tools page.

Earthdata Search

Earthdata Search is a tool for discovering Earth science data in NASA's Earth Observing System Data and Information System (EOSDIS) collection as well as in U.S and international agencies across the Earth science disciplines. Users (including those without specific knowledge of the data) can search for and read about data collections, search for data files by date and spatial area, preview browse images, and download or submit requests for data files. An Earthdata Login is required to download data.


In the project area, for some datasets, you can customize your granule. You can reformat the data and output as HDF, NetCDF, ASCII, KML, or GeoTIFF format. You can also choose from a variety of projection options. Lastly, you can subset the data, obtaining only the bands that are needed.

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Files in HDF and NetCDF format can be viewed using NASA's Panoply data viewer. Panoply is a cross-platform application that plots geo-referenced and other arrays. Additional functionality includes the ability to slice and plot arrays, combine arrays, and export plots and animations.

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Giovanni is an online environment for the display and analysis of geophysical parameters (Note: An Earthdata Login is required for full Giovani functionality). There are several options for analysis, including:

  • Time-averaged maps are a simple way to observe the variability of data values over a region of interest
  • Map animations are a means to observe spatial patterns and detect unusual events over time
  • Area-averaged time series are used to display the value of a data variable that has been averaged from all the data values acquired for a selected region for each time step
  • Histogram plots are used to display the distribution of values of a data variable in a selected region and time interval

For more detailed tutorials:

  • Giovanni How-To's on NASA's Goddard Earth Sciences Data and Information Services Center (GES DISC) YouTube channel
  • Data recipe for downloading a Giovanni map in NetCDF format and converting its data to quantifiable map data in the form of latitude-longitude-data value ASCII text
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The NASA Worldview visualization application provides the capability to interactively browse over 1,000 global, full-resolution satellite imagery layers and then download the underlying data. Many of the available imagery layers are updated within three hours of observation, which supports time-critical application areas such as wildfire management, air quality measurements, and flood monitoring. Imagery in Worldview is provided by NASA’s Global Imagery Browse Services (GIBS).

Worldview also includes imagery layers from the joint NASA/NOAA Geostationary Operational Environmental Satellite (GOES)-East and GOES-West satellites and from the Japan Meteorological Agency Himawari-8 satellite that are available at 10 minute increments for the last 30 days. These layers include Red Visible, which can be used for analyzing daytime clouds, fog, insolation, and winds; Clean Infrared, which provides cloud top temperature and information about precipitation; and Air Mass RGB, which enables the visualization of the differentiation between air mass types (e.g., dry air, moist air, etc.). These full disk hemispheric views allow for almost real-time viewing of changes occurring around most of the world.

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AppEEARS, available through NASA's Land Processes Distributed Active Archive Center (LP DAAC), offers a simple and efficient way to access and transform geospatial data from a variety of federal data archives. AppEEARS enables users to subset geospatial datasets using spatial, temporal, and band/layer parameters. Two types of sample requests are available: point samples for geographic coordinates and area samples for spatial areas via vector polygons.


Performing Area Extractions

After choosing to request an area extraction, you will be taken to the Extract Area Sample page where you will specify a series of parameters that are used to extract data for your area(s) of interest.

Spatial Subsetting

Define your region of interest in one of these three ways:

  • Upload a vector polygon file in shapefile format (you can upload a single file with multiple features or multipart single features). Files in .shp, .shx, .dbf, or .prj format must be zipped into a file folder to upload.
  • Upload a vector polygon file in GeoJSON format (can upload a single file with multiple features or multipart single features).
  • Draw a polygon on the map by clicking on the Bounding box or Polygon icons (single feature only).

Select the date range for your time period of interest.

Specify the range of dates for which you wish to extract data by entering a start and end date (MM-DD-YYYY) or by clicking on the Calendar icon and selecting dates a start and end date in the calendar.

Adding Data Layers

Enter the product short name (e.g., MOD09A1, ECO3ETPTJPL), keywords from the product long name, a spatial resolution, a temporal extent, or a temporal resolution into the search bar. A list of available products matching your query will be generated. Select the layer(s) of interest to add to the Selected layers list. Layers from multiple products can be added to a single request. Be sure to read the list of available products available through AppEEARS.

Selecting Output Options

Two output file formats are available:

  • GeoTIFF
  • NetCDF4

If GeoTIFF is selected, one GeoTIFF will be created for each feature in the input vector polygon file for each layer by observation. If NetCDF4 is selected, outputs will be grouped into files in .nc format by product and by feature.


Interacting with Results

Once your request is completed, from the Explore Requests page, click the View icon in order to view and interact with your results. This will take you to the View Area Sample page.

The Layer Stats plot provides time series boxplots for all of the sample data for a given feature, data layer, and observation. Each input feature is renamed with a unique AppEEARS ID (AID). If your feature contains attribute table information, you can view the feature attribute table data by clicking on the Information icon to the right of the Feature dropdown. To view statistics from different features or layers, select a different AID from the Feature dropdown and/or a different layer of interest from the Layer dropdown.


Be sure to check out the AppEEARS documentation to learn more about downloading the output GeoTIFF or NetCDF4 files.

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MODIS/VIIRS Subsetting Tools Suite

NASA's Oak Ridge National Laboratory DAAC (ORNL DAAC) has several MODIS and VIIRS Subset Tools:

  • The Global Subset Tool enables users to request a subset for any location on Earth, provided as GeoTIFF and in text format, including interactive time-series plots and more. Users specify a site by entering the site's geographic coordinates and the area surrounding that site, from one pixel up to 201 x 201 km. From the available datasets, users can specify a date and then select from MODIS Sinusoidal Projection or Geographic Lat/Long. Note: An Earthdata Login is required to request data.
  • The Fixed Subsets Tool enables users download pre-processed subsets for more than 3,000 field and flux tower sites for validation of models and remote sensing products. The goal of the Fixed Sites Subsets Tool is to prepare summaries of selected data products for the community to characterize field sites. It includes sites from networks such as National Ecological Observatory Network, Forest Global Earth Observatory network, Phenology Camera network, and Long Term Ecological Research Network that are of relevance to the biodiversity community.
  • The Web Service enables users to retrieve subset data (in real-time) for any location(s), time period, and area programmatically using a REST web service. Web service client and libraries are available in multiple programming languages, allowing integration of subsets into users' workflow.
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