From the replies so far, it seems that such an event although very rare,
is not unprecedented.
I hope the sequence comes to an end next month though, I would like
some warmth now!

Too right! Warmth is needed.

My tomato and cucumber seedlings in the greenhouse were doing fine until
about a week ago, but those cold nights have changed everything and they are
looking very sorry for themselves now and have stopped growing, especially
the cucumbers which are suffering from leaf curl due to the cold.

What a difference to last year! By now I was having to put the toms and cucs
outside because they had taken over the greenhouse and I needed the room for
other stuff.

This April has been quite exceptional compared to the last 5 years or so
because of the persistently cold nights which seems to do the most damage.
One or two chilly nights are OK but we've had a run from the 6th to the 18th
which has included 4 air frosts (7th - 10th) and not one min temp above
4.4C, mostly around 2C.

And what a cold, miserable day today.
________________
Nick G
Otter Valley, Devon
83 m amsl
http://www.ottervalley.co.uk