EPA's official open data catalog.

Environmental data from the EPA. See About the Data and Data Downloads.

Use the USGS EarthExplorer (EE) to search, download, and order satellite images, aerial photographs, and cartographic products. In addition to data from the Landsat missions and a variety of other data providers, EE provides access to MODIS land data products from the NASA Terra and Aqua missions, and ASTER level-1B data products over the U.S. and Territories from the NASA ASTER mission.

The world’s largest provider of weather and climate data. Land-based, marine, model, radar, weather balloon, satellite, and paleoclimatic are just a few of the types of datasets available.

World-wide marine environmental and ecosystem data.

U.S. Drought Portal - National Integrated Drought Information System

Search databases on toxicology, hazardous chemicals, environmental health, and toxic releases.

Authoritative scientific data and information about climate. Click on Maps & Data.

Monthly climate reports and climate data online: NCDC's archive of global historical weather and climate data in addition to station history information. These data include quality controlled daily, monthly, seasonal, and yearly measurements of temperature, precipitation, wind, and degree days as well as radar data and 30-year Climate Normals.

Climate datasets.