Import history from a CSV file

If your history is not in weewx or CumulusMX format, import it as a CSV. This covers Weather Display, WeatherCat, a Weather Underground history download, anything a logger can export, and a spreadsheet you kept by hand.

Everything is read in your browser. Only the values you map are sent, and anything already recorded live is left untouched, so it is safe to run again.

Before you start

History import needs a PRO subscription (the same entitlement as historical charts). A trial counts.

Step 1 - export a CSV

Any delimited text file works: comma, semicolon or tab separated, with or without a header row. One row per reading, one column per measurement.

Step 2 - pick the file

Open Connection on your site's dashboard and find Import history from a CSV file. Choose your file. The first few rows appear as a preview so you can see what we read.

Step 3 - map your columns

Column names we recognise (Out Temp, humidity, Barometer, Wind Speed and so on) are mapped for you. Fix anything we guessed wrong and leave what you do not have set to not in file.

Only the date / time column is required. Everything else is optional.

Step 4 - the three things no file states

These are the settings that matter, because nothing in a CSV says which is right:

Units. Only the unit families your mapping actually uses are asked for. Get this wrong and every value is off by a fixed factor.

Day first or month first. 03/08/2026 is 3 August to most of the world and 8 March in the United States. A wrong answer shifts months of history rather than failing loudly, so we never guess it. ISO dates (2026-08-03) are unambiguous and ignore this setting.

Rain: per reading or a running total. Cumulus-style exports write the day's running total in every row; summing that as if it were per-reading reports a month of rain as several metres. If your rain column climbs through the day and resets at midnight, choose Running total for the day.

Step 5 - import

The progress line shows rows sent and rows added. Rows already in your archive from live collection are skipped, so the two numbers differ when your file overlaps history you already have. Rows with an unreadable date, or with nothing usable once mapped, are counted as unusable and reported at the end.

If the upload is interrupted, run it again - progress is saved, and re-importing the same file adds nothing new.

What is imported

Temperature, humidity, dew point, wind speed, gust, direction, sea-level and station pressure, rainfall, rain rate, solar radiation, UV index, indoor temperature and humidity, PM2.5 and PM10.

Values that convert to something impossible (a temperature of 500 °C, a direction of 400°) are dropped rather than stored, and the rest of the row is kept.

Next steps

• Import from weewx
• Import from CumulusMX
• Correct a bad reading