Shaun Pudwell wrote:

My definition of a freezing day is a temperature less than or equal to 0.4C.

Shaun Pudwell.

Shaun,

The Met O definition of a freezing day is the same as a freezing night.
There must be a minus sign there or it doesn't count. -0.1C is, 0.0C is
not as 0.0C is the melting point of water, not the freezing point.

Between 0.0C and 0.4C equates to 0C (zero) rounded off.
Between -0.1C and -0.4C equates to -0C rounded off (minus zero, oft
maligned by the general public, but nevertheless significant)

The Met O rule of throwing to the nearest odd would round 0.5C to 1C
and -0.5C to -1C as you seem to suggest.

If you are looking at records of whole degrees, you should really only
include highs of M1C and below as freezing days as you would for night
frosts. That could well change your stats.

Best wishes, and I hope all your zeros are minuses!

Ken Cook, Copley, nr Barnard Castle, County Durham
http://mysite.wanadoo-members.co.uk/copley