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Your selected start date is after the end date

Daily

A daily timescale is best for showing changes that happen over a small amount of time. It allows us to see variations that would be otherwise lost when averaging out data over a larger amount of time.
Using a daily timescale is most useful when looking at a period of about a decade or less.

Monthly

Using a monthly timescale removes the large variations that can happen on a day-to-day basis. It can show more clearly gradual changes over the course of several months.
Using a monthly timescale is most useful when looking at a period of around a year, up to a few decades.

Yearly

A yearly timescale shows long term changes in the climate. By averaging over a whole year, the seasonal variations are removed allowing an easier comparison of year by year data.
Using a yearly timescale is most useful when looking at a period of a few years and upwards

For large timescales we will automatically change it to the most suitable, though you can still choose manually if you wish.

Start date

Select a date that you would like your data to start, some of the measurements in our archives go back over 180 years. For more information on when different measurements have been recorded, click here .

End date

If you would like to see a range of data, select an end date as well as a start date. However, if you would like to see a full record of just a single day, chose just a start date.

Here we are calculating the mean temperature as the mean value of the values recorded by the minimum and maximum thermometers.

For further information on the calculation of mean temperatures that takes into account factors such as systematic instrument error and extends our records further than is shown in this data, please see Air Temperatures at Armagh Observatory, Northern Ireland, From 1796 to 2002 from Dr. John Butler on our Publications page .