latest realtime map

Current and Evolving Conditions

What is EDDI?

The Evaporative Demand Drought Index (EDDI) is an experimental drought monitoring and early warning guidance tool. It examines how anomalous the atmospheric evaporative demand (E0; also known as "the thirst of the atmosphere") is for a given location and across a time period of interest. EDDI is multi-scalar, meaning that this period—or "timescale"—can vary to capture drying dynamics that themselves operate at different timescales; we generate EDDI at 1-week through 12-month timescales.

This webpage offers a frequently updated assessment of current conditions across CONUS, southern parts of Canada, and northern parts of Mexico; a tool to generate historical time series of EDDI for a user-selected region; introductions to the EDDI team; and a list of resources for users to explore EDDI and its applications further.

Why use EDDI?

EDDI can offer early warning of agricultural drought, hydrologic drought, and fire-weather risk by providing near-real-time information on the emergence or persistence of anomalous evaporative demand in a region. A particular strength of EDDI is in capturing the precursor signals of water stress at weekly to monthly timescales, which makes EDDI a strong tool for preparedness for both flash droughts and ongoing droughts.

How often is EDDI updated?

Currently, EDDI is generated daily—though with a 5-day lag-time—by analyzing a near-real-time atmospheric dataset. This lag-time results from the procedures to quality control the meteorological data used to estimate evaporative demand. There is also an ongoing effort to forecast EDDI based on seasonal climate-forecast information.


This work is supported in part by grants from (i) NOAA's Joint Technology Transfer Initiative (JTTI) for the project titled "Operationalizing an Evaporative Demand Drought Index (EDDI) service for drought monitoring and early warning;" (ii) NOAA's Sectoral Applications Research Program (SARP): Coping with Drought in Support of the National Integrated Drought Information System (NIDIS) program for the project titled "Developing a wildfire component for the NIDIS California Drought Early Warning System;" (iii) DOI's North Central Climate Science Center for the project (Grant #G14AP00182) titled "Ecological Drought, Climate Extremes and the Water Cycle across Timescales;" and (iv) Western Water Assessment, an NOAA RISA program, for the project titled "Enhancing the usability of EDDI," with funding originating from NIDIS.

Any issues with accessing the plots and other information on this page are welcome and should be sent to esrl.psd.data@noaa.gov.

NIDIS logo NOAA logo WWA logo CIRES logo CU logo WRCC logo NCCSC logo

Plot EDDI Maps of the Continental U.S.

If you use these plots in publications, we ask that you acknowledge the Physical Sciences Division. For example: "Image provided by the NOAA/ESRL Physical Sciences Division, Boulder, Colorado, from their web site at: https://www.esrl.noaa.gov/psd/."

Description of Maps and Underlying Data

The EDDI maps displayed here use atmospheric evaporative demand (E0) anomalies across a timescale of interest relative to its climatology to indicate the spatial extent and severity of drought. This page provides access to near-real-time (with a five-day latency, i.e., the most recent information is five days old) EDDI plots with timescales that measure E0 anomalies across the 1 to 12 weeks and 1 to 12 months prior to the most current date. The colors indicate the frequency at which the observed E0 anomaly has occurred in the climatology, with warm colors indicating conditions that are drier than normal and cool colors indicating wetter-than-normal conditions. As an example, the ED4 category indicates that the current E0 anomaly has only been observed less than 2% of the time in the past 38 years (1979-2016), which represents the most severe drought conditions; the EW4 category means indicates that the anomaly has been exceeded 98% of the time, which represents the wettest conditions. For plotting purposes, EDDI values are binned into different percentile categories analogous to the US Drought Monitor plots—however, in case of EDDI plots, both drought and anomalously wet categories are shown.

E0 is calculated using the Penman Monteith FAO56 reference evapotranspiration formulation, driven by temperature, humidity, wind speed, and incoming solar radiation from the operational North American Land Data Assimilation System (NLDAS-2) dataset. For a particular time-window, EDDI is estimated by standardizing the E0 anomalies relative to the the same accumulation time-window in the whole period of record (1979-present), using a rank-based non-parametric method described in Hobbins et al. (2016). EDDI data are available at a ~12-km resolution (0.125° lat and long) across CONUS since January 1, 1980, and are updated daily.

For more information regarding these plots and access to data, including customized EDDI maps, please contact Mike.Hobbins@noaa.gov (Phone: 303-497-3092)

How to read an EDDI map (pdf)

This is a Research and Development Application

Plot EDDI Time Series of the Continental U.S.

EDDI plot for Boulder, CO

This webtool allows a user to generate historical (1980-latest complete year) timeseries data of the Evaporative Demand Drought Index (EDDI) for a specified region in the Continental United States. The time series is generated as a table for different timescales, i.e. 1 to 12 months of integrated evaporative demand at the end of a given month. This tool also allows users to generate time series plots with user specified timescales.

1 Region
Drag to move map; SHIFT-Drag to select region
W   E
2 Plot Options
Averaging Period (Months)? Ending Month?
(ending month includes values through the end of that month)
Enter Region Title (OPTIONAL: Used in the plot title: default is the lat/lon range)

Description of Time-Series Data and Plot

This page generates historical (1980-latest complete year) time-series data of EDDI across a user-selected region and timescale. You can select your region as a rectangular area by directly entering latitude and longitude values or by selecting the area in the adjacent map. The main output is a table with EDDI time series for timescales of 1 to 12 months. A plot will also be generated with user- (or default-) entered month and averaging period, which will accompany another table showing the time-series data with user-defined specifications. On the output page, you will have an option to readily replot EDDI time series with different specifications.

To estimate evaporative demand (E0), this tool uses daily reference evapotranspiration based on the Penman Monteith FAO56 method for short reference crop that is available from the the operational North American Land Data Assimilation System (NLDAS-2) dataset. The spatial resolution of the data is 1/8th degree in latitude and longitude (i.e. approximately 12km). Daily E0 values are then aggregated to monthly values, and spatial averaging is done before monthly EDDI values are computed. At any point in time, there is large spatial variability in EDDI across CONUS. For generating these time series for meaningful assessment, we generally recommend that users select as small an area as possible (e.g., county, climate division, small watersheds), including point locations (i.e., by using a single latitude value in both the N and S boxes, and a single longitude value in both E and W boxes. for bounding the region, thereby getting the time series for just a single representative 12km x 12km pixel).

The main output table also includes reference evapotranspiration value (in mm) for each month used to calculate EDDI. The absolute values of E0 are highest during the warm season, during which there is also a heightened risk of water stress on the land surface in water-limited regions. For drought-related impacts, users can use time series of different EDDI timescales to compare with their own historical impacts data.

For further assistance or technical advice on the use of these timeseries data for research applications please contact Imtiaz.Rangwala@noaa.gov and Candida.Dewes@noaa.gov.

This is a Research and Development Application

EDDI Project Team

Joe Barsugli

Joe Barsugli  •  joeseph.barsugli@noaa.gov  •  303-497-6042

Joe is a Research Scientist at CIRES and NOAA’s Physical Sciences Division. Trained in climate theory and modeling, he works at the technical interface connecting climate science with the practitioners and technical staff who are informing planning for water and land management in the Colorado region, and connecting researchers to the problems faced by managers.
Candida Dewes

Candida Dewes  •  candida.dewes@noaa.gov  •  303-497-4236

Candida is a Research Scientist at NOAA’s Physical Sciences Division and CIRES/Western Water Assessment at the University of Colorado, Boulder. She has extensive research experience in climate variability and climate change and their impacts on socio-ecological systems. Her research with the North Central Climate Science Center focuses on regional-scale land surface processes contributing to drought, and in particular, the variability of evaporative demand under climate change. She is also interested in the role of rain versus snow in mountainous terrain how these precipitation types impact regional water resources. Before joining the NC CSC, she was a postdoc at the University of Virginia and Visiting Scholar at the National Center for Atmospheric Research, where she explored the climate impacts of land cover changes using NCAR’s Community Land Model. As a grad student at University of California, Santa Barbara, she investigated climate trends in Mexico and the impacts of climate variability on Mexican agriculture.
Mike Hobbins

Mike Hobbins  •  mike.hobbins@noaa.gov  •  303-497-3092

Since obtaining his Ph.D. in Hydrologic Science and Engineering from Colorado State University in 2004, Mike has worked in research into evapotranspiration, evaporative demand, and drought. As a Research Scientist for NOAA’s Physical Sciences Division and the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado in Boulder, CO, his recent work supports drought early warning across the US for the National Integrated Drought Information Systems (NIDIS) and famine early warning across the globe for the Famine Early Warning Systems Network (FEWS NET), including the development and dissemination of reanalyses of evaporative demand; the development of the Forecast Reference Evapotranspiration (FRET) product for daily and weekly evaporative demand forecasts across the US; and the development of the EDDI.
Justin Huntington

Justin Huntington  •  justin.huntington@dri.edu  •  775-673-7670

Justin Huntington is an associate research professor of Hydrology at the Desert Research Institute, Reno, Nevada. His research interests are focused on remote sensing, land surface energy balance measurement and modeling, drought monitoring, and hydrologic modeling. His research primarily supports water use, water demand, and drought mapping and prediction efforts funded by the U.S. Bureau of Reclamation, U.S. Geological Survey, U.S. Bureau of Land Management, NASA, NOAA, and Google. He is one of 25 members of the 2012-2017 Landsat Science Team.
Jeff Lukas

Jeff Lukas  •  lukas@colorado.edu  •  303-735-2698

Jeff is a Research Integration Specialist with the Western Water Assessment program at CIRES, based out of the University of Colorado Boulder. For the past 15 years, Jeff has worked closely with water managers and other resource decision-makers in the Rocky Mountain West to help them understand and prepare for climate-related vulnerabilities by interpreting and applying paleoclimate data, historical climate records, and climate projections. He was lead author of the 2014 Climate Change in Colorado report for the Colorado Water Conservation Board, which summarized the latest science on climate trends and projections for the state. Jeff was initially trained in forest ecology (M.S., Forestry, University of Montana) and conducted fire history research, later shifting into applied climatology and hydrology.
Daniel McEvoy

Daniel McEvoy  •  daniel.mcevoy@dri.edu  •  775-673-7682

Daniel is a researcher with the Western Regional Climate Center. His research interests are interdisciplinary and span the fields of climate, hydrology, and meteorology. They include advancing drought monitoring technology, seasonal drought prediction, the role of evaporative demand on drought, quality and uncertainty assessment of weather observations, and climate modeling.
Charles Morton

Charles Morton  •  charles.morton@dri.edu  •  775-673-7620

Charles Morton is an assistant research scientist at the Desert Research Institute in Reno, NV. His research interests include surface energy balance modeling, hydrology, remote sensing, and cloud computing. For the past 10 years he has worked on numerous projects estimating evapotranspiration in the western United States using satellite remote sensing.
Imtiaz Rangwala

Imtiaz Rangwala  •  imtiaz.rangwala@noaa.gov  •  303-497-6544

Imtiaz is a research scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder and NOAA’s Physical Sciences Division. He is a climate scientist with training in assessing and diagnosing regional scale climate change. Using climate observations and models, he works to understand and quantify climate processes relevant to regional warming trends and hydrological processes changes. This specifically ties into understanding climate extremes and changes in water balance in the western U.S., including the Great Plains region, and the how these extremes affect ecosystem response. Other work includes developing approaches to addressing and incorporating future climate change uncertainty into decision-making and climate adaptation.
Heather Yocum

Heather Yocum  •  heather.yocum@noaa.gov  •  303-497-3917

Heather is a Research Scientist at the University of Colorado and NOAA’s Cooperative Institute for Research in Environmental Sciences (CIRES) in Boulder, CO. An environmental anthropologist and political ecologist, Dr. Yocum studies how culture and social systems impact the way that humans understand and interact with the environment. Since earning her PhD in Anthropology from Michigan State University in 2013, she has researched the production and use of climate and weather information to support natural resource management and decision-making; changing patterns of land use and natural resource management in the face of climate change; and environmental markets and payments for ecosystem services.


Related Links


  • Michael Hobbins, Andrew Wood, Daniel McEvoy, Justin Huntington, Charles Morton, Martha Anderson, and Christopher Hain (June 2016): The Evaporative Demand Drought index: Part I – Linking Drought Evolution to Variations in Evaporative Demand. Journal of Hydrometeorology, 17(6),1745-1761, doi:10.1175/JHM-D-15-0121.1.
  • Daniel J. McEvoy, Justin L. Huntington, Michael T. Hobbins, Andrew Wood, Charles Morton, Martha Anderson, and Christopher Hain (June 2016) The Evaporative Demand Drought index: Part II – CONUS-wide Assessment Against Common Drought Indicators. Journal of Hydrometeorology, 17(6), 1763-1779, doi:10.1175/JHM-D-15-0122.1.