The variability of the onset of spring in Britain

The first day of spring is defined in terms of daily maximum temperatures. Spring at Oxford as defined begins some time between the third week of February and the last week of April. The average date shows a secular change over the last hundred years. The date of the first day of spring is shown to be related to ice conditions in the Baltic and in the Iceland area, to the sea temperature pattern in the North Atlantic, the circulation patterns at 500 mb and to various atmospheric indices. Rules developed from these relationships enable ‘statistical’ forecasts for the first day of spring to be made.