* Demand pegged 8 pct above seasonal norms
* Rough withdrawals halved on Feb. 28
* Power rises on cold, exports to France
LONDON, Feb 20 (Reuters) - British prompt gas prices fell on Wednesday as withdrawals from gas storage sites helped the market meet higher demand levels that were driven by a drop in temperatures.
Day-ahead gas shed 0.20 pence to 67.35 pence per therm in early trading, while gas for within-day delivery traded at 67.15 pence.
"Demand is higher today and should be high for the rest of this week. It looks like there's adequate supply around though from storage," said one gas market analyst at a utility.
UK gas demand was pegged 8 percent above seasonal norms on Wednesday morning as temperatures dropped 3 degrees Celcius below average levels, prompting higher use of gas-fired heating systems.
Britain's Hornsea, Rough and Holford gas storage sites were adding supply to the market early on Wednesday, helping meet higher demand levels and leaving the system around 11 million cubic metres per day (mcm/d) long.
Rough gas storage, Britain's largest, will reduce withdrawal capacity by half on Feb. 28 from 0000-1200 GMT, operator Centrica (LSE: CNA.L - news) said.
The site will also undergo its annual maintenance shutdown from Sept. 7-24.
Day-ahead contracts also calculated in a drop in gas flows through the Teesside terminal as operator BP (LSE: BP.L - news) planned an outage until Feb. 23 on the CATS Riser platform in the North Sea.
The outage was expected to cut flows through the terminal by around 4 mcm/d, according to Thomson Reuters Point Carbon analysts.
Weather conditions are expected to remain cold until next week, while early March could see a return to milder conditions, Britain's Met Office said.
Front-month March changed hands at 66.05 pence, up 0.10 pence on Tuesday's close.
Further out, curve contracts traded higher, with benchmark front-season gas adding 0.20 pence to 63.90 pence.
Cold weather and exports to continental Europe lifted UK power prices, traders said.
Baseload day-ahead power changed hands at 50.60 pounds per megwatt-hour, while March traded at 48.10 pounds.
"Day-ahead power is holding up so far on the colder weather and potential exports to the continent," one UK power trader said, adding that France was expected to need more electricity from Britain. (Reporting by Karolin Schaps; Editing by Alison Birrane)
