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 US ASOS (2000-) and Iowa AWOS (1995-2011) sites. This archive simply provides the as-is collection of historical observations, very little quality control is done. More details on this dataset are here.

Data Sources: The data made available on this page is sourced from a number of places including: Unidata IDD, NCEI ISD, and MADIS One Minute ASOS.


Python Script Examples
fetch by network
selectively fetch

R Script Examples
A community user has contributed R language version of the python script. There is also a riem R package allowing for easy access to this archive.

This archive contains processed observations up until 2024-06-17T07:11:28Z. Data is synced from the real-time ingest every 10 minutes.

Backend documentation exists for those that wish to script against this service.

Select Network

1) Select Station/Network by clicking on location:

If you select no stations, you can download up to a 24 hour period of all data available from this archive!

2) Select From Available Data:

Note: Precipitation data is unavailable for non-US sites. The Heat Index/Wind Chill value retroactively use current NWS equations.

3) Select Date Range:

Note: These dates define timestamps starting at midnight of the selected timezone. The start date is inclusive and the end date is exclusive.

Start Date:
End Date:

4) Timezone of Observation Times:

The following options are available for how the observation time is presented.

5) Download Options:

Data Format:

Include Latitude + Longitude?

Include Elevation (meters)?

How to represent missing data?

How to represent Trace reports?

6) Limit Report Types

See news item on recent changes made for report types. When in doubt, pick both routine and specials.

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 *true* 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)
Peak Wind Gust (from PK WND METAR remark) (knots)
Peak Wind Gust Direction (from PK WND METAR remark) (deg)
Peak Wind Gust Time (from PK WND METAR remark)
unprocessed reported observation in METAR format