I can't remember which engine manufacturer it was, but I read in a technical document by them that all their carburettor based engines could be subject to icing at up to 32C.
There is the CAA safety sense document
http://www.caa.co.uk/docs/33/ga_srg_...L14October.pdf which has a diagram showing the same thing.
Also, as pointed out by Graybeard, where an engine can suffer from carb icing even at full power.