Check Your Weather Station
Upload an export from your personal weather station and this page pulls the nearest airport station (ASOS) and nearby CoCoRaHS rain gauges for the same days, lines them up hour by hour, and tells you where your station agrees and where it drifts. The Neighbors tab shows live readings around you right now. Everything runs in your browser; your file never leaves your device.
1 · Where is your station?
Tap the map to move the pin. Rounded to about 100 m is plenty — the tool only uses it to find the nearest reference stations.
2 · Upload your station export
Ecowitt, Weather Underground, WeeWX, Davis WeatherLink, Ambient, or any CSV with a time column
No file loaded.
Columns found (fix anything that's wrong)
3 · Pick the reference station
Nearest active ASOS/AWOS airport stations from the Iowa Environmental Mesonet. Closer is better, but a station at a very different elevation or on the other side of a ridge may not be the best twin.
| Choose a state and location to list stations. |
Verdict
Side by side
Scatter (1:1 line = perfect)
Average difference by hour of day
A warm afternoon bump usually means sun hitting the sensor or radiation shield. A cold pre-dawn dip often means the station sits in a cold-air pocket — that one can be real weather, not an error.
Daily rain
ASOS days run midnight to midnight local time. CoCoRaHS observers read their gauge around 7 AM, so their value for a date covers the 24 hours ending that morning — your station is re-totaled the same way for that comparison.
Live readings near you
Latest observations from airport (ASOS/AWOS) and road-weather (RWIS) stations within the radius, from the Iowa Environmental Mesonet. Uses the location and state from the Compare tab.
Pull your reading automatically from an Ecowitt station (optional, bring your own keys)
Keys are sent only to api.ecowitt.net from your browser and are forgotten when you close this tab. Create them in your Ecowitt account under User Profile → Private Center.
How the comparison works
- Your file is read in the browser. The tool looks for a time column and the usual weather columns (outdoor temperature, dew point, humidity, wind, gust, pressure, rain, solar) and guesses units from the headers. You can correct any of it in the column table.
- Reference data is fetched live from the Iowa Environmental Mesonet: hourly routine observations from the ASOS you chose for exactly the days in your file, plus daily totals from the nearest active CoCoRaHS observers.
- Hour by hour matching. Each ASOS hourly observation is paired with your reading closest in time (within 7 minutes). Averages are not used, so a single bad reading shows up rather than hiding.
- Statistics. Bias = your station minus the reference (positive means you read high). MAE is the typical size of the difference, r is how well the two move together.
What counts as "good"?
| Variable | Good | Check | Why a difference can be real |
|---|---|---|---|
| Temperature | |bias| < 1 °F | > 2 °F | Cold pockets at night, urban heat, a different elevation. |
| Dew point | |bias| < 2 °F | > 4 °F | Humidity sensors drift high after a few years, especially in fog. |
| Humidity | |bias| < 5 % | > 10 % | Same as dew point. |
| Wind | ratio 0.5–1.0 | < 0.4 | Airport anemometers sit at 10 m in the open; home sensors are lower and sheltered, so reading lower is normal. |
| Pressure | |bias| < 0.02 inHg | > 0.05 | Usually just a calibration offset you can enter in your console. |
| Rain | within 10 % | > 25 % low | Summer storms can drop very different totals a few miles apart; look at many days, not one. |
Data sources
Iowa Environmental Mesonet (Iowa State University) for ASOS observations, station lists and CoCoRaHS daily reports; CoCoRaHS volunteers; OpenStreetMap contributors for the map. Optional: Ecowitt API with your own keys.