The digitised database includes calibrated data from 1838-1904 to 2001-2004 (depending on the parameter; see below). The data after that cut-off has not yet been corrected for instrumental sensitivity, exposure of the instruments or the time of observation; it is copied directly from our record books.
Data from 1853 onwards is also held in the Met Office database along with other historic stations (Armagh data is here). Much of the historic data for Armagh is held at the Public Record Office Northern Ireland (PRONI) as well, with start dates in the 1860s and 1870s for most types of data.
Unless otherwise specified (e.g. ‘evening wet bulb’), all readings were taken in the morning on any given day. Since 1938, the standard has been 09:00 GMT, but this has varied between 08:27 and 10:27 GMT over the earlier years. Rainfall is measured between two consecutive morning readings, whereas sunshine is measured midnight to midnight. Evening readings were taken around 21:00 GMT, but the standard changed, like the morning one, so the reading time varied from 20:27 to 22:27 GMT. Such matters are discussed in more detail in the relevant Publications.
01/01/1838 to 31/12/2001
Morning present/dry bulb: 02/01/1838 to 31/12/2004
Morning wet bulb: 02/01/1838 to 31/12/2004
Evening present/dry bulb: 01/01/1844 to 08/03/1965
Evening wet bulb: 01/01/1844 to 08/03/1965
Daily minimum: 01/01/1844 to 31/12/2004
Daily maximum: 01/01/1844 to 31/12/2004
30 cm depth: 21/04/1904 to 31/12/2002
100 cm depth: 21/04/1904 to 31/12/2002
21/04/1880 to 31/12/2004
This includes measurements of the same parameters as above from the stated end date until the present day, with the exception of evening measurements, which were discontinued in 1965. Additionally, the following parameters are shown (either as part of the daily summary or as a graph):
Grass minimum temperature:
01/07/2000 to present
Pressure at 9am GMT:
01/01/1850 to present
Humidity (calculated from dry and wet bulb)
Morning humidity: 02/01/1838 to 31/12/2004
Evening humidity: 03/01/1844 to 31/12/1965
Wind speed: 01/07/2000 to present
Wind direction: 01/07/2000 to present
Total cloud: 01/07/2000 to present
Visibility: 01/07/2000 to present
Present weather/weather at observation: 01/07/2000 to present
State of ground: 01/07/2000 to present
If you chose to explore data for a single day, ‘Show scans’ option will appear if available. If a single date is chosen under the advanced option, the relevant scans from the corresponding month will be displayed under ‘More data’, if available. This only stretches as far back as the digitised data (i.e. January 1838); for a more comprehensive view of the scanned record books, see Scans of Record Books below.