The IEM maintains an ever growing archive of automated airport weather observations from around the world! These observations are typically called 'ASOS' or sometimes 'AWOS' sensors. A more generic term may be METAR data, which is a term that describes the format the data is transmitted as. If you don't get data for a request, please feel free to contact us for help. The IEM also has a one minute interval dataset for Iowa ASOS (2000-) and AWOS (1995-2011) sites. This archive simply provides the as-is collection of historical observations, very little quality control is done. "M" is used to denote missing data.
1) Select Station/Network by clicking on location:
2) Select From Available Data:
3) Specific Date Range (If needed):
Note: There is up to an hour delay for observations to appear within this service. A process runs at approximately 20 minutes after the hour to copy over the previous hour's worth of data in the backend database behind this service.
4) Timezone of Observation Times:
The following options are available for how the observation time is presented.
5) Download Options:
Include Latitude + Longitude?
How to represent missing data?
How to represent Trace reports?
6) Limit Report Types
This attempts to filter the downloaded data
to only include those reports you want. In the future, this will deliniate
between routine and special obs. Select the report types to include.
7) Finally, get Data:
Download Variable Description
ASOS User's Guide has detailed information about these data variables. The value "M" represents either value that was reported as missing or a value that was set to missing after meeting some general quality control check, or a value that was never reported by the sensor. The METAR format makes it difficult to determine which of the three cases may have happened.
- three or four character site identifier
- timestamp of the observation
- Air Temperature in Fahrenheit, typically @ 2 meters
- Dew Point Temperature in Fahrenheit, typically @ 2 meters
- Relative Humidity in %
- Wind Direction in degrees from north
- Wind Speed in knots
- One hour precipitation for the period from the observation time to the time of the previous hourly precipitation reset. This varies slightly by site. Values are in inches. This value may or may not contain frozen precipitation melted by some device on the sensor or estimated by some other means. Unfortunately, we do not know of an authoritative database denoting which station has which sensor.
- Pressure altimeter in inches
- Sea Level Pressure in millibar
- Visibility in miles
- Wind Gust in knots
- Sky Level 1 Coverage
- Sky Level 2 Coverage
- Sky Level 3 Coverage
- Sky Level 4 Coverage
- Sky Level 1 Altitude in feet
- Sky Level 2 Altitude in feet
- Sky Level 3 Altitude in feet
- Sky Level 4 Altitude in feet
- Present Weather Codes (space seperated)
- Apparent Temperature (Wind Chill or Heat Index) in Fahrenheit
- Ice Accretion over 1 Hour (inches)
- Ice Accretion over 3 Hours (inches)
- Ice Accretion over 6 Hours (inches)
- unprocessed reported observation in METAR format