* Day-ahead price down
* System oversupplied by 15.8 mcm
* Milder temperatures seen from Feb. 20
LONDON, Feb 10 (Reuters) - British wholesale natural gas prices declined on Wednesday morning due to oversupply, as domestic production rose after the end of terminal and pipeline maintenance.
Gas for next-day delivery was down 0.25 pence at 29.10 pence per therm at 0920 GMT from the previous settlement, while gas for immediate delivery was 0.15 pence lower at 28.85 p/therm.
Britain's gas system was oversupplied by 15.8 million cubic metres (mcm), with demand forecast at 314 mcm - above the seasonal norm of 287 mcm - and supply at 329.8 mcm, National Grid data showed.
Flows from the UK Continental Shelf have increased after planned maintenance in the North Sea was completed. The send-out of liquefied natural gas has also risen.
"There was maintenance at St Fergus (gas terminal) and Entry SEGAL (pipeline system) this week, but that all finished yesterday so supply has picked up," a gas trader said.
Temperatures are forecast to decline by a couple of degrees Celsius by the weekend, according to Britain's Met Office.
In the Netherlands, the day-ahead gas price at the TTF hub dipped by 0.11 euro per megawatt-hour to 12.07 euros/MWh.
In the European carbon market, front-year EU allowances declined by 0.18 euro to 4.79 euros a tonne.
(Reporting by Nina Chestney; Editing by Jan Harvey)