Weather conditions have been unusually warm over the winter months in large parts of southeastern Europe, as well as in Turkey.
As a result, winter crop hardening remains weaker than normal in these regions, according the latest EU Mars Bulletin report.
Winter hardening is a bio-physical process whereby winter cereals gain low-temperature tolerance to withstand freezing conditions that occur during the winter dormancy period.
There are now fears that frost damage has since occurred on these crops after the return of cold weather.
The affected areas include northern Romania and the central Balkans, northern Spain and northwestern Turkey.
Crops in some of these areas are covered by a layer of snow, which may provide some protection.
The areas affected by frost kill will become apparent in the coming weeks.
Elsewhere, crops are reported as being in relatively good conditions across much of Europe.