Two more water companies have been granted drought orders following a government decision.
Southern Water, which covers large areas of south-east England, was granted the order for Kent and Sussex.
A single order has also been made for the entire Mid Kent Water area. Both water companies have said they will not use the orders yet.
Environment minister Ian Pearson said: "Recent rainfall has not reduced the need for restrictions."
Mr Pearson, who granted the orders, said: "The rainfall we are seeing now and over the rest of the summer will have little impact on groundwater levels."
He said at this time of year the effects of evaporation and the uptake of water from growing plants means most of the rain does not reach natural underground storage.
Les Dawson, chief executive of Southern Water, said the recent wet weather means the company will not implement the order immediately, but the situation was still serious.
"Some underground water sources are running at near record low levels. Therefore the restrictions might have to be introduced later this year," he said.
Mr Pearson added that although reservoirs were nearly full the region relies on groundwater for at least 70% of its supply.
Mid Kent Water's asset director Paul Seeley said: "Customers can be assured that we are doing all that we can to protect supplies and that we will not hesitate to introduce further restrictions as necessary."
Both companies submitted drought order applications on 20 March following independent inspections.
The first non-essential use drought order for over a decade was granted to Sutton and East Surrey Water earlier this month.
The government said no other companies have so far submitted drought order applications, or indicted that they intend to.
Mr Pearson said all three companies had succeeded in meeting leakage targets, but expected to see continued efforts from all the companies to improve leakage.