We have had daffodils flowering on the Isle of Wight for the last 3 weeks but this week, although it has been a real taste of winter due to northerly winds blowing across our Island, spring officially arrived at 0:08 on Wednesday 21st March.
In climate terms, spring begins on the 1st of March, as March, April and May are the 3 months we use when we look at seasonal climate data.
However, astronomically, spring starts on the vernal equinox. In astronomy, an equinox is the event when the Sun is directly above the equator of the earth and occurs on or around 20/21 March and 22/23 September when the astronomical day and night are equal. The word equinox derives from the Latin words aequus (equal) and nox (night).
There are also two solstices during the year, when the Sun reaches its furthest distance from the equator. The summer Solstice or longest day, is when the Sun reaches its most northern position and occurs around the 20/21 June. The winter solstice or shortest day is when the Sun reaches its most southerly position and occurs on 21/22 December.
The actual day of the equinox or solstice varies because of variation in the rotational axis of the Earth. The axis is not fixed; it exhibits a slow, but steady precession through the years.
The dates for these events this year are below:
Spring equinox : 21/3/07 at 00:07
Summer solstice: 21/6/07 at 18:06
Autumn equinox: 23/3/07 at 09:51
Winter solstice: 22/12/07 at 06:08