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Data & Maps

Historical Data and Conditions

By looking back at historical data, communities can get a better understanding of the drought and extreme weather threats to be prepared for. The resources below help document and quantify historical drought conditions in order to help inform planning. Three historical drought datasets can be explored side by side: the U.S. Drought Monitor (weekly, 2000–present); Standardized Precipitation Index (monthly, 1895–present); and June-July-August Palmer Modified Drought Index values from tree-ring reconstructions and instrumental data (yearly, 0–2017).

54.8%

of the U.S. was in drought in September 2012, according to the U.S. Drought Monitor record since 2000

66.2%

of the lower 48 states were in drought in Summer 1934, the most in the lower 48, according to the Living Blended Drought Product since year 0

22.9%

of the U.S. was in Exceptional Drought (D4) in February 1977, according to the Standardized Precipitation Index (SPI) since 1895

82.3%

of the U.S. was Abnormally Wet in May 2019, the most according to the Standardized Precipitation Index (SPI) since 1895

Explore Historical Drought Conditions

U.S. Drought Monitor (2000 - Present)

9-Month SPI (1895 - Present)

Paleoclimate Data (0 - 2017)

U.S. Drought Monitor Category

% of U.S.

9-Month Standardized Precipitation Index (SPI)

% of U.S.

Palmer Modified Drought Index (PMDI) - Paleoclimate Data

% of U.S.

The U.S. Drought Monitor (2000–present) depicts the location and intensity of drought across the country. Every Thursday, authors from NOAA, USDA, and the National Drought Mitigation Center produce a new map based on their assessments of the best available data and input from local observers. The map uses five categories: Abnormally Dry (D0), showing areas that may be going into or are coming out of drought, and four levels of drought (D1–D4). Learn more.

Drought results from an imbalance between water supply and water demand. The Standardized Precipitation Index (SPI) measures water supply, specifically precipitation. SPI captures how observed precipitation (rain, hail, snow) deviates from the climatological average over a given time period—in this case, over the 9 months leading up to the selected date. Red hues indicate drier conditions, while blue hues indicate wetter conditions. Data are available monthly from 1895–present. Learn more.

In paleoclimatology, proxy climate data (e.g., tree rings, ocean sediments) can allow us to reconstruct past climate conditions before we had widespread instrumental records. By combining tree-ring reconstructions and instrumental records, the Living Blended Drought Atlas estimates average drought conditions (the Palmer Modified Drought Index, or PMDI, shown here) for each June–August as far back as the year 0. Red hues indicate drier conditions, while blue hues indicate wetter conditions.

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SOURCE(S):

NOAA, USDA, National Drought Mitigation Center

SOURCE(S):

NOAA's National Centers for Environmental Information

SOURCE(S):

NOAA's National Centers for Environmental Information

Data and Map Gallery

Representative image of the U.S. Drought Monitor

U.S. Drought Monitor (USDM)

NOAA and its partners publish regional reports each quarter, summarizing weather, impacts and predictions.

2000 - present

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An example Palmer Modified Drought Index reconstruction map for 1782 CE.

Living Blended Drought Atlas (LBDA) - Historical Drought Information

The Living Blended Drought Atlas (LBDA) is a recalibrated data series of June-July-August Palmer Modified Drought Index (PMDI) values by United States climate division, compiled by blending tree-ri

Historical data

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text (ascii)

netcdf-4

Paleoclimatology Data

NCEI provides the paleoclimatology data and information scientists need to understand natural climate variability and future climate change.

Historical data

Example map of Europe showing June-August PDSI in 1540

Old World Drought Atlas

The OWDA provides new data to determine the causes of Old World drought and wetness and attribute past climate variability to forced and/or internal variability.

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text (ascii)

netcdf-4

Global Historical Climatology Network mapping system showing PMDI

Global Historical Climatology Network (GHCN)

Global Historical Climatology Network (GHCN): an integrated database of daily climate summaries from land surface stations across the globe, including a common suite of quality assurance reviews.&n

1832 - Present (not all data available for all periods)

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text (ascii)

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Historical Water Watcher

This tool, available as part of The Climate Toolbox, provides maps and summary tables of different drought types, such as agricultural and meteorological drought, for a location in the contiguous U

Current Conditions, Historical data (period of record varies)

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Historical Data and Conditions