Climate Atlas

Visit the Climate Atlas User Manual for step-by-step instructions on creating maps, selecting variables, downloading data, and other application features of the Climate Atlas tool.

Yes, you can explore and compare climate patterns across regions. 

The Climate Atlas includes a Compare Maps feature, which allows you to view two maps side by side to evaluate differences across locations, variables, or time periods. This is especially useful for identifying regional patterns or changes over time. Step-by-step instructions are available in the Climate Atlas User Manual. 

When comparing locations, the most important consideration is to be aware of the dataset being used. For example, results from the global ERA5 dataset may differ from those based on the nClimGrid dataset due to variations in dataset methodology, spatial resolution, and underlying data sources. These differences reflect how datasets are constructed, not just climate variability. Refer to the Climate Atlas Data Information Sheet for more information on the source datasets. 

Differences in terrain or climate zones should be considered when interpreting results.

The Climate Atlas tool is built on scientifically vetted climate datasets that support detailed mapping and decision-making. These datasets provide extensive historical coverage, rigorous quality control via NOAA processes, and consistent spatial resolution. Together, they ensure accurate, reliable, and up-to-date temperature and precipitation information. For more information, see the What quality assurance measures are in place for the data? and the Is this data certifiable? FAQ sections. 

Core datasets include: 

• For the contiguous U.S: nClimGrid-Daily and nClimGrid-Monthly 
• For global coverage: ERA5-Land and ERA5 

For detailed information on dataset characteristics, methodology, variables, and complementary NOAA tools and products, please refer to the Climate Atlas Data Information Sheet. 

Data Limitations 

Some data and map types (e.g., Annual Events’ freeze dates, Thresholds) rely on standardized definitions that may not apply equally across all regions. For map-specific definitions, assumptions, and nuances (such as how variables, thresholds, or time ranges are calculated), use the Tooltips directly within the application, which provides context-sensitive guidance. 

Climate Normals (For more information, see FAQ: What are Climate Normals?) are based on fixed climatological reference periods and are not continuously updated in the same way as daily or monthly datasets, since they represent standardized baseline conditions rather than real-time observations.

 Additional limitations include: 

• Data is gridded and may not reflect localized conditions or microclimates 
• Spatial resolution may smooth terrain-driven variability 
• Coverage (For more information, see FAQ: What geographic areas are covered?) and resolution vary by dataset and Map Type (e.g., Averages and Totals, Normals, or Anomalies and Ranks) 
• Timescale (For more information, see FAQ: What time periods are available?), Base Period, and calendar options are subject to change depending on Map Type, Variable, and Timescale selected 

Update Schedule 

The Climate Atlas tool automatically updates as new data becomes available: 

• Daily data: On an approximate five-day delay 
• Monthly data: Updated with an approximate 2-month delay 

To ensure high data quality and consistency, datasets may be retroactively updated as additional observations are received and quality control processes are applied. As a result, previously displayed values may change over time. 

Each map includes information on when the data was last updated, to assess data recency and versioning when interpreting results.

Maps are based on gridded datasets, which display temperature and precipitation across uniform grid cells. 

• Each grid cell represents an average over an area (e.g., several kilometers), not an exact location 
• Local factors such as elevation, terrain, land use, vegetation, and urban development can influence conditions in ways that are not fully captured
• Microclimates (e.g., valleys, coastlines, or urban heat islands) may experience different conditions than the surrounding grid cell 
• Differences may also occur when comparing gridded data to individual weather station observations 

For the most accurate interpretation, use the Climate Atlas tool to understand regional patterns and trends, and consider supplementing with local observations when site-specific detail is important. 

For more information on how ERA5 and nClimGrid datasets were generated, reference the ERA5 Documentation or the nClimGrid Documentation. For more information on how these datasets were incorporated into the Climate Atlas tool, see the Climate Atlas Data Information Sheet.

The Climate Atlas tool provides data for multiple regions. Spatial resolution and available variables vary by dataset and map type: 

• Contiguous U.S. (CONUS) 
  • Includes full historical coverage for all products 
  • Normals maps are available for CONUS only 
• Global land areas 
  • U.S. states, commonwealths, and territories: includes Alaska, Hawai’i, Puerto Rico, U.S. Virgin Islands, Guam, Northern Mariana Islands, American Samoa 
  • Available for select products using the ERA5 reanalysis dataset (generally 1950–present). Spatial resolution and available variables may differ from CONUS products 
• Global oceans 
  • Available for Threshold maps only, but time coverage is limited (generally ~2010–present) due to dataset constraints and consistent global reanalysis availability

Time coverage varies by dataset. Refer to the Climate Atlas Data Information Sheet for dataset time periods and coverage ranges. 

Available time options may differ by dataset and are shown in the application’s Timescale menu: 

• 1 Day 
• 1 Week 
• Month: includes 1-, 3-, and 6-month periods 
• Seasonal (meteorological): For more information, see FAQ: How does the Climate Atlas tool define the start and end of a season?
• 1 Year: January 1 through December 31 of the selected year 
• Month-to-date: the first day of the month through the selected day (e.g., May 1 – May 12) 
• Year-to-date: from January 1 through the selected day (e.g., January 1 – May 12) 
• Year-to-month: cumulative monthly values from January 1 through the end of the selected month (e.g., January 1 – May 31) 

Base Periods 

Climate Normals and anomaly-based products use a defined Base Period (typically a 30-year reference window) rather than a single year range. This base period may vary depending on the dataset and product configuration and is especially important when interpreting Normals, since they are not tied to a single calendar year.

Climate Normals are typically a special set of 15- or 30-year averages for temperature and precipitation computed for a specific set of locations across the country. Normals provide information about the expected values for temperature and precipitation for a day, month, season, or year. Values can be used to compare current weather for a location with this special average to determine if conditions are warmer/cooler/wetter/drier than average and by how much. 

For more information, see the Understanding Climate Normals FAQ, which provides detailed guidance on calculating and interpreting climate normals. 

In the Climate Atlas tool, Normals maps are available for the contiguous U.S. only, and are not continuously updated in the same way as daily or monthly datasets, since they represent standardized baseline conditions rather than real-time observations. Climate Atlas utilizes the following base periods: 

• 1991–2020: The current official 30-year U.S. Climate Normals period. NCEI updates Climate Normals every 10 years, and this period is used for the most common applications, including comparing current conditions to a standardized climate baseline. 
• 1901–2000: A longer-term benchmark used for climate monitoring and reporting applications, including comparisons used to understand climate over the past century. 
• 2006–2020: A supplemental 15-year Normals period designed for users who need a baseline that more closely reflects recent climate conditions.

Anomalies and ranks help place temperature and precipitation values in a historical context. Interpretation may vary by region, season, and dataset. 

• Anomalies show the difference from a long-term average (baseline period) 
  • Positive anomalies indicate warmer or wetter conditions; negative anomalies indicate cooler or drier conditions 
  • Example: A user might select to map the maximum temperature anomalies over the week of April 11, 2026, from the base period 1991-2020. If a grid point on the map indicates a value of 0°F, that indicates that, averaged over the course of the week of April 11 to April 17, 2026, the maximum daily temperature for that grid point was equal to the conditions found for that same week over the 1991-2020 base period. 
• Ranks compare values across the full historical record, from lowest to highest 
  • A higher rank indicates one of the most extreme values (e.g., warmest or wettest), while lower ranks indicate cooler or drier conditions 

For additional explanation of how anomalies, ranks, and base periods are defined, refer to the in-application tooltips. For additional information on how these are calculated, refer to the supporting documentation: Anomalies vs. Temperature and Climatological Rankings.

Degree Days measure how much air temperatures deviate from 65°F, a baseline commonly used to estimate heating and cooling demand. 

• Heating Degree Days: When temperatures fall below 65°F, heating Degree Days accumulate, indicating a need for heating. 
  • 65°F - Daily Mean Temperature = Heating Degree Days 
• Cooling Degree Days: When temperatures rise above 65°F, cooling Degree Days accumulate, indicating a need for cooling. 
  • Daily Mean Temperature - 65°F = Cooling Degree Days 

Rather than counting actual days, Degree Days represent the cumulative difference from this baseline over time, making them especially useful for estimating energy demand. Annual totals are typically the most relevant for building design and long-term planning, while shorter time periods can help highlight seasonal variability. These maps are commonly used in energy planning, architecture, and operations to better understand climate-driven demand.

Annual Events maps show the timing of key climate events within a year. These maps help illustrate when important meteorological milestones typically occur and how they vary across locations. 

Available Annual Events: 

• First Freeze Of The Fall/Winter Season (For more information, see FAQ: How are first/last freeze dates calculated? How does the Climate Atlas tool define the start and end of a season?) 
• Last Freeze Of The Winter/Spring Season 
• Warmest Day Of The Year 
• Coldest Day Of The Year

NOAA’s meteorological seasons are defined by full calendar months:

• Winter: December–February 
• Spring: March–May 
• Summer: June–August 
• Fall: September–November 

These definitions follow Northern Hemisphere conventions; because seasons are reversed in the Southern Hemisphere, labels like “summer” and “winter” may not align with local conditions. For global analyses, interpret seasonal maps based on the calendar months included, not just the season name.

Freeze dates are based on daily minimum temperatures, where a freeze occurs at or below 32°F (0°C). To ensure all events are captured (even in regions where freezing can occur year-round) the Climate Atlas tool uses a standardized “climate year” to avoid missing early or late freeze events and maintain consistency across regions: 

• First freeze: the first occurrence of ≤32°F between July 16 (target year) and July 15 (following year) 
• Last freeze: the last occurrence of ≤32°F between July 16 (previous year) and July 15 (target year) 

Important Considerations 

• Freeze-free periods may be very short in colder climates, affecting interpretation. 
• Values are based on gridded air temperature, not local ground conditions or microclimates. 
• These maps are most reliable for the Northern Hemisphere, low elevation, and non-Arctic regions. Interpretations of seasonal data in the Southern Hemisphere or high latitudes are less certain (For more information, see FAQ: How does the Climate Atlas tool define the start and end of a season?).

Yes, you can download maps as JPEG, PDF, or PNG, or access the data as cloud-optimized GeoTIFFs on the web application (For more information, see FAQ: Can the data be integrated with GIS platforms?). See the Climate Atlas User Manual for further instructions. For access to large datasets and metadata, see the NOAA Open Data Dissemination (NODD) cloud environment; for instructions on using the NODD cloud bucket, see the data access documentation.

Yes, data can be downloaded as cloud-optimized GeoTIFF files, a standard format compatible with common GIS tools such as ArcGIS and QGIS. These files support geospatial workflows including layering, clipping, reprojection, and spatial analysis. File sizes and resolution may require appropriate computing resources, especially for large-area or long-term analyses. Review dataset metadata and projections to ensure proper alignment within their GIS environment. 

Larger datasets and metadata are available through the NOAA Open Data Dissemination (NODD) cloud environment for scalable workflows (instructions on using the NODD cloud bucket are available in the data access documentation).

Complementary NOAA tools and products are provided within the Climate Atlas Data Information Sheet.

Climate Atlas data is derived from authoritative, quality-controlled datasets and is produced using established, peer-reviewed NOAA scientific methodologies (refer to the Climate Atlas Data Information Sheet for more information on the source datasets). The datasets support scientific research, analysis, and decision-making and undergo rigorous quality assurance processes to help ensure accuracy, consistency, and reliability. 

Most datasets available through the Climate Atlas tool have previously been used in other NOAA products, including the legacy U.S. Climate Atlas and U.S. Maps applications. A limited number of datasets, including the Annual Events (For more information, see FAQ: What are Annual Events?) and Thresholds datasets, are being made publicly available through the Climate Atlas for the first time. These datasets are developed using the same scientific methods and quality assurance practices as the other NOAA datasets. NOAA continuously evaluates and improves its data products. If you identify a potential issue or have questions about a dataset, please refer to the FAQ "How do I provide feedback on the data?" for information on submitting feedback.

The outputs generated by the Climate Atlas tool are provided for informational and research purposes only. Users are responsible for independently evaluating the suitability of the information for their specific applications. 

Climate Atlas data is derived from authoritative, quality-controlled datasets and is appropriate for scientific research, analysis, and decision support. However, outputs generated directly within the Climate Atlas application are not considered certified products for regulatory or legal purposes. NOAA does not guarantee that outputs from the Climate Atlas tool meet requirements for certification, regulatory approval, or legally binding determinations. 

For users requiring certified data, formally published and archived datasets may meet certification or regulatory standards, depending on the use case. Users should refer to official dataset documentation in the Climate Atlas Data Information Sheet, or the data access search tool to determine suitability.

If you use data, maps, or outputs from the Climate Atlas tool in a publication, you should cite the tool and the date accessed, since maps and data are continuously updated. When exporting maps, any included source links or attribution information should be retained to support transparency and reproducibility. 

A recommended citation format is: 

NOAA National Centers for Environmental Information (NCEI).Climate Atlas. Accessed YYYY-MM-DD. https://www.ncei.noaa.gov/maps/climate-atlas/

Reference the Climate Atlas metadata page associated with the map or dataset used for detailed information on data sources, processing methods, versioning, and update history to support reproducibility. If a metadata page is not yet available, refer to the Climate Atlas Data Information Sheet for information on the source datasets.

If your publication requires dataset-level attribution, also include the relevant underlying datasets used by the map (linked directly through the metadata page or described in the Climate Atlas Data Information Sheet): 

Dataset Author(s). (Year). Dataset Name (Version if applicable). Accessed via Climate Atlas, YYYY-MM-DD. National Centers for Environmental Information (NCEI), NOAA. 

For reproducibility, include key metadata details, such as the selected dataset, variable, time period, spatial extent, and any relevant parameters or map settings.

Source information for each dataset is provided within the Climate Atlas Data Information Sheet, and these are the best contacts for issues with data quality or structure. 

• For nClimGrid-Daily and nClimGrid-Monthly datasets: contact NOAA’s National Centers for Environmental Information at ncei.orders@noaa.gov. 
• For ERA5 and ERA5-Land datasets: the European Centre for Medium-Range Weather Forecasts can be contacted via their support page.

NOAA has completed quality assurance and validation checks on this product. If you notice any discrepancies or issues, please complete the product survey. 

To provide feedback that improves NOAA’s mission to deliver and disseminate information nationwide, please complete the product survey by opening the Climate Atlas tool and selecting the “Help improve this product” button at the bottom right of the screen.