Out of interest what is the latest somewhere in the UK didn't record a temperature above 0C all day? If I had to guess I'd say sometime around the 10th April, but I have no idea or any idea where to find such information.

15th and/or 16th April 1966 had an ice day in Kent (on the North Downs, altitude 120+m) and saw 6" of snow accumulate. 

Don't know for the UK but for here the latest ice day was 19th March 1930. There hasn't been any ice days in March since at least 1965.

March 2013 delivered a load of them. There were 10 national  I think in that whole month.

My latest was the weekend of the 24th/25th. Snow lay on the ground all day and a layer of stratocumulus ensured the sun didn't shine for several days keeping the temperature at 0C or below for at least 2 if not 3 days.

I didn't think that was possible round my part of the country so late in March.

April 1966 is the month to look at

Various locations in Wales recorded a maximum of 0.0C on 14th and 15th

Various locations in Northern Ireland recorded a maximum of 0.0C on 15th and 16th

Details can be found by going to this link http://www.metoffice.gov.uk/public/weather/climate-extremes/#?tab=climateExtremes

Can't say when the latest date was for Scotland as the lowest maximum in April shown by the link above was -1C on the 8th in 1975. But temperatures below 0C were no doubt recorded later than this in 1966.

From the 14th-15th April 1966 a vigorous depression brought heavy snow to much of southern England in a cold NE wind from Hampshire to Kent (rain in the SW). Some places saw continuous snow for nearly 48 hours. Depths of 4-6 inches were widely reported.

So it looks like the latest ice day ever recorded is probably around 16th April.

Here are the reanalysis charts from 0z 15th April 1966 from WZ

Rrea00119660415.gif

Rrea00219660415.gif

Notable for a complete reversal of North Atlantic flow at our latitude. Pity I was too young to really recall the event!

Don't think that April 1966 was as exceptional in Scotland as in Southern England. 8th April 1975 had a max of only 1C here and is the coldest April day in the last 55 years at least. 14th & 15th April 1966 had maxes of 3C here.

Did anywhere record an ice day in the cold spell which occurred in late April 1981? (Think it was 81).

I don't think so. The maps of maximum temperature in the daily weather summary for April 1981 show maximums of +1C in several locations on the 24th and 26th. So close but not quite an ice day.

Nottingham Watnall recorded a temperature between 0.0C and 2.1C throughout the period from early on the 24th to late on the 26th.

Metoffice has a 1.6C maximun on the 1st May in the Highlands 1979.

Still any advances on 16th April 1966 for the latest ice day on record?

Did a bit more digging

The temperature at Eskdalemuir reached a maximum of 32F on 26th April 1919 with a minimum of 21F.

I only have the temperature to the nearest whole Fahrenheit degree so can't say whether it meets the definition of an ice day as being no higher than 0.0C. But it is close enough.

That's amazing - No way would that be possible at a lowland site in England. I reckon what we saw in March 2013 must be the latest date possible. March 25th in wide areas of East Anglia it didn't get above 0C .

Well the 16th April 1966 was definitely an ice day for lowland S England, so that is the one currently to beat.

GWs 26th April is a good candidate but cannot be completely verified. 

how about during the exceptional snowfall in late apr 1908 i wonder?

I did look at April 1908. Only have data for a limited number of stations. None were that close to an ice day. Coldest maximum I could find was 36F. I'm sure that was not the coldest but likelihood of an ice day anywhere probably very low.