Gardeners in central, eastern and southern Britain have been warned to brace themselves for hosepipe bans.
The damp Christmas failed to provide sufficient rainfall to replenish depleted reservoirs.
Environment Agency chiefs said Lincolnshire, Cambridgeshire, parts of Bedfordshire and Northamptonshire, and west Norfolk were already in drought because of last year’s dry spring and autumn.
It warned that water shortages “may lead to more drought permits” while “restrictions on public water supplies remain possible”.
South East Water urged gardeners to invest in water butts and use rainwater.
Its Ardingly reservoir is just 37 per cent full, and Arlington is 60 per cent full.
Spokesman Lee Dance said it would take “prolonged rainfall over coming winter months” to return resources to normal.
Anglian Water, which in November was granted a drought order to top up its Pitsford Reservoir (54 per cent full) with river water, has now been granted a second order by the Environment Agency.
Its Rutland reservoir is 62 per cent full, but the order will allow it to extract water from the River Nene to top it up.
Spokeswoman Ciaran Nelson said the weather was “record-breaking” and added: “The Environment Agency says rainfall has been at its lowest yearly level since 1921.”
Thames Water’s Richard Aylard said: “We don’t get into drought because of a dry week, month or year. Sixteen of the last 21 months have seen below average rainfall. There is a very real risk of summer drought.”