Anglian Water said the hosepipe ban will remain in place despite recent wet weather.
The company said the restriction was being reviewed on a daily basis but underground water levels remained low across the region.
Seven water firms across southern and eastern England brought in restrictions in April after two dry winters.
Anglian Water said the region was the driest in the country and one wet month would not counteract a dry year.
The hosepipe bans were followed by record rainfall across the UK in April and more in May.
When the bans were introduced, the companies warned they could last past the autumn and possibly into the winter.
But the latest drought briefing from the Environment Agency said the wet weather had significantly reduced the risk of drought and widespread water restrictions this summer.
Despite Thames Water saying it could lift its hosepipe ban sooner than expected, Anglian said customers still needed to help safeguard water supplies.
Peter Simpson, managing director of Anglian Water, said: "The possibility of a warm summer and a third dry winter is still a concern for our region. The very wet few weeks we experienced in April followed two exceptionally dry years, and most importantly, two dry winters.
"That long, dry spell left water levels in reservoirs, rivers and underground aquifers significantly below normal - and in some cases historically low.
"Almost half of the water we put into supply comes from groundwater sources, particularly in the east of our region. The full impact of the recent rain on these sources remains to be seen, largely because our aquifers refill naturally and more slowly.
"We don't want to keep the hosepipe ban in place for a day longer than we have to, and we're keeping the situation under constant review. However, restrictions remain in place for now."
Anglian Water supplies water and wastewater services to more than six million customers in the east of England and Hartlepool.