Though it's a bit early this year, it's a regular occurrence in London. I call it the False Spring. During March, we get a startling break from the cold/grey/rain (and a bit of snow these last few years) and suddenly, it feels like Spring. The daffodils and other bulbs optimistically poke their heads through the dead leaves, the sun shines, the temperature soars to 55f and everyone feels good again. It's a great thing.
Unfortunately it seems to generally be followed by an April shower or sixty (that's roughly two showers a day mind) and things get a bit chilly again before starting to look bright, possibly, around mid-May.
I say make hay while the sun shines, but just don't let yourselves be broken-hearted when our False Spring disappears for awhile. Just count the sunny days while you can!