The Reference Climatological Stations (RCS) network represents the first effort by NOAA to create and maintain a nationwide network of stations located only in areas where no changes in the surroundings are foreseen. Efforts to establish the network began in 1954 by the National Weather Service. The network became operational in 1966 with the selection of fifteen stations from a list of 28 candidate sites; six more were added as the network expanded. Most stations were located at university agricultural experiment stations. Core data elements include temperature, rainfall, and wind speed & direction. Some stations also measured evaporation and soil temperature. Observations were taken daily by volunteer observers, and were a subset of the extensive NWS Cooperative Observations network. Stations were assigned Cooperative Station IDs, but were provided with special forms on which to record wind speed and direction, elements not recorded at other Coop stations.

The Reference Climatological Stations (RCS) network represents the first effort by NOAA to create and maintain a nationwide network of stations located only in areas where no changes in the surroundings are foreseen. Efforts to establish the network began in 1954 by the National Weather Service. The network became operational in 1966 with the selection of fifteen stations from a list of 28 candidate sites; six more were added as the network expanded. Most stations were located at university agricultural experiment stations. Core data elements include temperature, rainfall, and wind speed & direction. Some stations also measured evaporation and soil temperature. Observations were taken daily by volunteer observers, and were a subset of the extensive NWS Cooperative Observations network. Stations were assigned Cooperative Station IDs, but were provided with special forms on which to record wind speed and direction, elements not recorded at other Coop stations.

The State of the Climate is a collection of periodic summaries recapping climate-related occurrences on both a global and national scale. The State of the Climate Monthly Overview - Upper Air report describes tropospheric and stratospheric temperatures, with data placed into historical perspective. Temperatures above the Earth's surface are measured within the lower troposphere, middle troposphere, and stratosphere using in-situ balloon-borne instruments (radiosondes) and polar-orbiting satellites. Global Upper Air reports are available monthly from May 2000, with annual summary reports starting in 2001. The report became completely automated (eliminating the narrative section) in 2014.

Local Climatological Data (LCD) contains summaries from major airport weather stations that include a daily account of temperature extremes, degree days, precipitation amounts and winds. Also included are the hourly precipitation amounts and abbreviated 3-hourly weather observations. This is the final quality controlled copy and generally has a one to two month time lag. The local climatological data annual file is produced from the National Weather Service (NWS) first and second order stations. These data are contained in the LCD monthly and annual publications. The monthly summaries include maximum, minimum, and average temperature, temperature departure from normal, dew point temperature, average station pressure, ceiling, visibility, weather type, wet bulb temperature, relative humidity, degree days (heating and cooling), daily precipitation, average wind speed, fastest wind speed/direction, sky cover, and occurrences of sunshine, snowfall and snow depth. The annual summary with comparative data contains monthly and annual averages of the above basic climatological data in the meteorological data for the current year section, a table of the normals, means, and extremes of these same data, and sequential table of monthly and annual values of average temperature, total precipitation, total snowfall, and total degree days. Also included is a station location table showing in detail a history of, and relative information about, changes in the locations and exposure of instruments. The NCDC also archives a Preliminary Local Climatological Data manuscript that contains similar information, but is not quality controlled.

These daily weather records were compiled from a subset of stations in the Global Historical Climatological Network (GHCN)-Daily dataset. A weather record is considered broken if the value exceeds the maximum (or minimum) value recorded for an eligible station. A weather record is considered tied if the value is the same as the maximum (or minimum) value recorded for an eligible station. Daily weather parameters include Highest Min/Max Temperature, Lowest Min/Max Temperature, Highest Precipitation, Highest Snowfall and Highest Snow Depth. All stations meet defined eligibility criteria. For this application, a station is defined as the complete daily weather records at a particular location, having a unique identifier in the GHCN-Daily dataset. For a station to be considered for any weather parameter, it must have a minimum of 30 years of data with more than 182 days complete in each year. This is effectively a 30-year record of service requirement, but allows for inclusion of some stations which routinely shut down during certain seasons. Small station moves, such as a move from one property to an adjacent property, may occur within a station history. However, larger moves, such as a station moving from downtown to the city airport, generally result in the commissioning of a new station identifier. This tool treats each of these histories as a different station. In this way, it does not thread the separate histories into one record for a city. Records Timescales are characterized in three ways. In order of increasing noteworthiness, they are Daily Records, Monthly Records and All Time Records. For a given station, Daily Records refers to the specific calendar day: (e.g., the value recorded on March 7th compared to every other March 7th). Monthly Records exceed all values observed within the specified month (e.g., the value recorded on March 7th compared to all values recorded in every March). All-Time Records exceed the record of all observations, for any date, in a station's period of record. The Date Range and Location features are used to define the time and location ranges which are of interest to the user. For example, selecting a date range of March 1, 2012 through March 15, 2012 will return a list of records broken or tied on those 15 days. The Location Category and Country menus allow the user to define the geographic extent of the records of interest. For example, selecting Oklahoma will narrow the returned list of records to those that occurred in the state of Oklahoma, USA. The number of records broken for several recent periods is summarized in the table and updated daily. Due to late-arriving data, the number of recent records is likely underrepresented in all categories, but the ratio of records (warm to cold, for example) should be a fairly strong estimate of a final outcome. There are many more precipitation stations than temperature stations, so the raw number of precipitation records will likely exceed the number of temperature records in most climatic situations.

These daily weather records were compiled from a subset of stations in the Global Historical Climatological Network (GHCN)-Daily dataset. A weather record is considered broken if the value exceeds the maximum (or minimum) value recorded for an eligible station. A weather record is considered tied if the value is the same as the maximum (or minimum) value recorded for an eligible station. Daily weather parameters include Highest Min/Max Temperature, Lowest Min/Max Temperature, Highest Precipitation, Highest Snowfall and Highest Snow Depth. All stations meet defined eligibility criteria. For this application, a station is defined as the complete daily weather records at a particular location, having a unique identifier in the GHCN-Daily dataset. For a station to be considered for any weather parameter, it must have a minimum of 30 years of data with more than 182 days complete in each year. This is effectively a 30-year record of service requirement, but allows for inclusion of some stations which routinely shut down during certain seasons. Small station moves, such as a move from one property to an adjacent property, may occur within a station history. However, larger moves, such as a station moving from downtown to the city airport, generally result in the commissioning of a new station identifier. This tool treats each of these histories as a different station. In this way, it does not thread the separate histories into one record for a city. Records Timescales are characterized in three ways. In order of increasing noteworthiness, they are Daily Records, Monthly Records and All Time Records. For a given station, Daily Records refers to the specific calendar day: (e.g., the value recorded on March 7th compared to every other March 7th). Monthly Records exceed all values observed within the specified month (e.g., the value recorded on March 7th compared to all values recorded in every March). All-Time Records exceed the record of all observations, for any date, in a station's period of record. The Date Range and Location features are used to define the time and location ranges which are of interest to the user. For example, selecting a date range of March 1, 2012 through March 15, 2012 will return a list of records broken or tied on those 15 days. The Location Category and Country menus allow the user to define the geographic extent of the records of interest. For example, selecting Oklahoma will narrow the returned list of records to those that occurred in the state of Oklahoma, USA. The number of records broken for several recent periods is summarized in the table and updated daily. Due to late-arriving data, the number of recent records is likely underrepresented in all categories, but the ratio of records (warm to cold, for example) should be a fairly strong estimate of a final outcome. There are many more precipitation stations than temperature stations, so the raw number of precipitation records will likely exceed the number of temperature records in most climatic situations.

In March 2015, data for thirteen Alaskan climate divisions were added to the NClimDiv data set. Data for the new Alaskan climate divisions begin in 1925 through the present and are included in all monthly updates. Alaskan climate data include the following elements for divisional and statewide coverage: average temperature, maximum temperature (highs), minimum temperature (lows), and precipitation. The Alaska NClimDiv data were created and updated using similar methodology as that for the CONUS, but with a different approach to establishing the underlying climatology. The Alaska data are built upon the 1971-2000 PRISM averages whereas the CONUS values utilize a base climatology derived from the NClimGrid data set. In January 2025, the National Centers for Environmental Information (NCEI) began summarizing the State of the Climate for Hawaii. This was made possible through a collaboration between NCEI and the University of Hawaii/Hawaii Climate Data Portal and completes a long-standing gap in NCEI's ability to characterize the State of the Climate for all 50 states. NCEI maintains monthly statewide, divisional, and gridded average temperature, maximum temperatures (highs), minimum temperature (lows) and precipitation data for Hawaii over the period 1991-2025. As of November 2018, NClimDiv includes county data and additional inventory files In March 2015, data for thirteen Alaskan climate divisions were added to the NClimDiv data set. Data for the new Alaskan climate divisions begin in 1925 through the present and are included in all monthly updates. Alaskan climate data include the following elements for divisional and statewide coverage: average temperature, maximum temperature (highs), minimum temperature (lows), and precipitation. The Alaska NClimDiv data were created and updated using similar methodology as that for the CONUS, but with a different approach to establishing the underlying climatology. The Alaska data are built upon the 1971-2000 PRISM averages whereas the CONUS values utilize a base climatology derived from the NClimGrid data set. As of November 2018, NClimDiv includes county data and additional inventory files.

This dataset replaces the previous Time Bias Corrected Divisional Temperature-Precipitation Drought Index. The new divisional data set (NClimDiv) is based on the Global Historical Climatological Network-Daily (GHCN-D) and makes use of several improvements to the previous data set. For the input data, improvements include additional station networks, quality assurance reviews and temperature bias adjustments. Perhaps the most extensive improvement is to the computational approach, which now employs climatologically aided interpolation. This 5km grid based calculation nCLIMGRID helps to address topographic and network variability. This data set is primarily used by the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC) to issue State of the Climate Reports on a monthly basis. These reports summarize recent temperature and precipitation conditions and long-term trends at a variety of spatial scales, the smallest being the climate division level. Data at the climate division level are aggregated to compute statewide, regional and national snapshots of climate conditions. For CONUS, the period of record is from 1895-present. Derived quantities such as Standardized precipitation Index (SPI), Palmer Drought Indices (PDSI, PHDI, PMDI, and ZNDX) and degree days are also available for the CONUS sites. In March 2015, data for thirteen Alaskan climate divisions were added to the NClimDiv data set. Data for the new Alaskan climate divisions begin in 1925 through the present and are included in all monthly updates. Alaskan climate data include the following elements for divisional and statewide coverage: average temperature, maximum temperature (highs), minimum temperature (lows), and precipitation. The Alaska NClimDiv data were created and updated using similar methodology as that for the CONUS, but with a different approach to establishing the underlying climatology. The Alaska data are built upon the 1971-2000 PRISM averages whereas the CONUS values utilize a base climatology derived from the NClimGrid data set. As of November 2018, NClimDiv includes county data and additional inventory files.

The dataset consists primarily of U.S. surface airways observations (SAO) data beginning in 1965 and extending through 1981. Note that a few stations have already had certain years within this 1965-81 period re-keyed as hourly. For these stations, only a subset of the period was keyed. In addition, other stations did not have data keyed at all during this period, or during the periods immediately before or after the 1965-81 range. These stations data have been keyed to as thoroughly as possible complete their entire period of record back to July, 1948. The major data variables are as follows: WBAN Identification Station Number, observational type, ceiling and cloud, visibility, present weather, temperature, relative humidity, wind, pressure and precipitation. The observations are generally recorded for the 24 hour period midnight to midnight. The keying format was designed to reflect the data as entered on the page to make keying easier for the key entry personnel, who were not trained meteorological technicians. The "raw" observations which comprise this dataset will be quality checked to include data adjustments and converted to NCDC's Integrated Surface Hourly (ISH) format.

The dataset consists primarily of U.S. surface airways observations (SAO) data beginning in 1965 and extending through 1981. Note that a few stations have already had certain years within this 1965-81 period re-keyed as hourly. For these stations, only a subset of the period was keyed. In addition, other stations did not have data keyed at all during this period, or during the periods immediately before or after the 1965-81 range. These stations data have been keyed to as thoroughly as possible complete their entire period of record back to July, 1948. The major data variables are as follows: WBAN Identification Station Number, observational type, ceiling and cloud, visibility, present weather, temperature, relative humidity, wind, pressure and precipitation. The observations are generally recorded for the 24 hour period midnight to midnight. The keying format was designed to reflect the data as entered on the page to make keying easier for the key entry personnel, who were not trained meteorological technicians. The "raw" observations which comprise this dataset will be quality checked to include data adjustments and converted to NCDC's Integrated Surface Hourly (ISH) format.