* Within-day gas rose 3.5 pence, or 6.8 percent, to 55 pence per therm at 0840 GMT

* Day-ahead gas was up 1.0 pence at 59.25 pence per therm

* Within-day prices had fallen 24 percent between Dec. 24 and New Year's Eve as industrial demand fell during the holiday period and the weather remained broadly temperate

* The average temperature forecast for the day was slashed by 5.3 degrees Celsius to 3.1 degrees

* Average temperatures are expected to drop further on Thursday, to 1.6 degrees Celsius

* As a result, demand for residential gas, used primarily in heating homes, has jumped to 225 million cubic metres (mcm)on Wednesday from 165 mcm on Monday

* Nevertheless, the gas system was oversupplied, with demand forecast at 310.4 mcm per day and flows seen at 338.4 mcm, National Grid data showed

* Norwegian gas flows to Britain were up 5 mcm at 106 mcm while British offshore gas production was also 5 mcm higher at 113 mcm

* Liquefied natural gas (LNG) sendout rates are also expected to rise to 51 mcm, 13 mcm higher than Monday

* One LNG tanker arrived on Monday with another expected Sunday and one more is expected on Tuesday

* Peak wind generation however was low at 3.7 gigawatts (GW) on Wednesday and 1.6 GW on Thursday compared with metred capacity of 12 GW and generation levels above 9 GW earlier this week

* The Heysham 1-2 nuclear reactor went offline on Wednesday for planned maintenance work, a week earlier than planned

* This brings the capacity of reactors offline to 2.6 GW of about 9 GW overall

* Day-ahead Dutch gas at the TTF hub rose 0.45 euro to 21.50 euros per megawatt hour

* The benchmark Dec-19 EU carbon contract rose 0.6 euro to 25.61 euros per tonne