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.

Tools/Libaries

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 2026-11-09T23:41:31Z. Data is synced from the real-time ingest every 10 minutes.

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

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! If you select stations, the aggregate request limit is 1,000 station years worth of data.

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.

station:
three or four character site identifier
valid:
timestamp of the observation
tmpf:
Air Temperature in Fahrenheit, typically @ 2 meters
dwpf:
Dew Point Temperature in Fahrenheit, typically @ 2 meters
relh:
Relative Humidity in %
drct:
Wind Direction in degrees from *true* north
sknt:
Wind Speed in knots
p01i:
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.
alti:
Pressure altimeter in inches
mslp:
Sea Level Pressure in millibar
vsby:
Visibility in miles
gust:
Wind Gust in knots
skyc1:
Sky Level 1 Coverage
skyc2:
Sky Level 2 Coverage
skyc3:
Sky Level 3 Coverage
skyc4:
Sky Level 4 Coverage
skyl1:
Sky Level 1 Altitude in feet
skyl2:
Sky Level 2 Altitude in feet
skyl3:
Sky Level 3 Altitude in feet
skyl4:
Sky Level 4 Altitude in feet
wxcodes:
Present Weather Codes (space seperated)
feel:
Apparent Temperature (Wind Chill or Heat Index) in Fahrenheit
ice_accretion_1hr:
Ice Accretion over 1 Hour (inches)
ice_accretion_3hr:
Ice Accretion over 3 Hours (inches)
ice_accretion_6hr:
Ice Accretion over 6 Hours (inches)
peak_wind_gust:
Peak Wind Gust (from PK WND METAR remark) (knots)
peak_wind_drct:
Peak Wind Gust Direction (from PK WND METAR remark) (deg)
peak_wind_time:
Peak Wind Gust Time (from PK WND METAR remark)
metar:
unprocessed reported observation in METAR format

Publications Citing IEM Data (View All)

These are the most recent 10 publications that have cited the usage of data from this page. This list is not exhaustive, so please let us know if you have a publication that should be added.