The Comparative Climatic Data (CCD-2018) tables of meteorological elements outline the climate conditions at major U.S. weather observing stations, Puerto Rico, and the Pacific Islands. These data come from active observing sites that are currently in use, as well as former sites with comparable exposure. The observed data tables omit stations that have less than three years of data for the current operating site. The Normals, Means, and Extremes table contained in the Local Climatological Data Annual Summary for individual stations is part of this publication.
The stations list is alphabetically by state. The table is arranged to allow the user to compare the values for different locations in a single table of the same elements. Some elements will not be in the table for weather stations that do not regularly report that element. Asterisks (*) denote average frequency of occurrence greater than zero but smaller than one-half.
Some of the data provided here are based on data exchanged under the World Meteorological Organization (WMO) World Weather Watch Program according to WMO Resolution 40 (Cg-XII). This allows WMO member countries to place restrictions on the use or re-export of their data for commercial purposes outside of the receiving country. Those countries’ data summaries and products which are available here and are intended for free and unrestricted use in research, education, and other non-commercial activities. For non-U.S. locations, the data or any derived product shall not be provided to other users or be used for their re-export for commercial services.
The Observed Data values are the means and extremes for the period of record (number of years) indicated. Periods of record are documented in the Local Climatological Data annual publications.
- Temperature: Highest of Record, °F
- Temperature: Lowest of Record, °F: The annual temperature entry for each station represents the highest or lowest observed temperature in any month.
- Mean Number of Days Maximum Temperature 90°F or Higher
- Mean Number of Days Minimum Temperature 32°F or Less: The mean number of days with a minimum temperature of 32°F or lower indicates the frequency of occurrence of days with freezing temperatures.
- Mean number of Days with Precipitation 0.01 Inches or More: This table shows the mean number of days per month with at least 0.01 inch of precipitation. This is the smallest amount of precipitation numerically recorded, and it includes the liquid water equivalent of frozen precipitation. The frequency of days with precipitation should not be considered as the frequency of cloudy days.
- Snowfall (Including Ice Pellets and Sleet):Average total in inches. Beginning in April 1988, hail is also included under snowfall, which means that some stations may show snowfall during the warmmonths.
- Wind: Average Speed (MPH): The average wind speed is based on the speed of the wind regardless of direction.
- Wind: Maximum Speed (MPH): This table expresses both a maximum wind speed for the stations and, where available, the direction (referenced to true North) from which it blew. Short gusts are listed only for stations denoted with a (G). If the direction is expressed as one of the 16 compass points (N, NNE, NE, etc.) the maximum speed is calculated from the minimum time during which one mile of wind passed the station. Note that some stations that report short gusts (G) may also use the 16 compass point reference for wind direction. If the direction is expressed numerically, the maximum speed is the highest one minute average value recorded by the observer. Direction is given in tens of degrees clockwise from true North.
- Sunshine: Average Percent of Possible: The total time that sunshine reaches the surface of Earth is expressed as the percentage of the maximum amount possible from sunrise to sunset with clear sky conditions.
- Sunshine - Average Percent of Possible (Cities Listed by Ranking Most to Least)
- Cloudiness: Mean Number of Days (Clear, Partly Cloudy, Cloudy): This table shows the mean number of days per category of cloudiness. The categories are determined for daylight hours only. Clear denotes zero to 3/10 average sky cover. Partly cloudy denotes 4/10 to 7/10 average sky cover. Cloudy denotes 8/10 to 10/10 average sky cover.
- Average Relative Humidity: Morning (M), Afternoon (A): The relative humidity is expressed as a percentage measure of the amount of moisture in the air compared to the maximum amount of moisture the air can hold at the same temperature and pressure. Average humidity values are given for selected morning and afternoon observations. Maximum relative humidity values usually occur during morning hours. In this publication, the Local Standard Time (LST) of morning and afternoon humidities are shown below:
- Atlantic, Alaskan (M morning 8 a.m.) (Afternoon 2 p.m.)
- Eastern, Bering, 165°W Meridian (M morning 7 a.m.) (Afternoon 1 p.m.)
- Central, 180°E Meridian (M morning 6 a.m.) (Afternoon NOON)
- Mountain, 165°E Meridian (M morning 5 a.m.) (Afternoon 5 p.m.)
- Pacific, 150°E Meridian (M morning 4 a.m.) (Afternoon 4 p.m.)
- 135°E Meridian (M morning 9 a.m.) (Afternoon 3 p.m.)
Note: The tables below contain the 1981–2010 Climate Normals data. Normals are updated decennially, for the most recent 30-year period. If an instrument's exposure was changed, mathematical adjustments are made to make the data representative of the current location. The values are statistically determined and cannot be recreated solely from the original record.
- Normal Daily Maximum Temperature, °F: The maximum temperature data are the normal daily values for each month. They have been adjusted as necessary.
- Normal Daily Minimum Temperature, °F: The minimum temperature data are the normal daily values for each month. They have been adjusted as necessary.
- Normal Daily Mean Temperature,°F: The mean temperature data are the normal daily values for each month. They have been adjusted as necessary.
- Normal Heating Degree Days (July–June) Base 65 °F: Degree day data are used to estimate amounts of energy required to maintain comfortable indoor temperature levels. Daily values are computed from each day's mean temperature (max + min/2). Each degree that a day's mean temperature is below or above 65°F is counted as one heating or cooling degree day.
- Normal Cooling Degree Days (January–December) Base 65 °F: The normal precipitation is the arithmetic mean for each month over the 30-year period, adjusted as necessary, and includes the liquid water equivalent of snowfall.
- Normal Precipitation, Inches: The normal precipitation is the arithmetic mean for each month over the 30-year period, adjusted as necessary, and includes the liquid water equivalent of snowfall.