* Spot prices at highest point since 2008
* Output down by as much as 2.2 bcfd
* California says feels shortages
* Noble gets cold weather boost in Israel
HOUSTON, Feb 6 (Reuters) - Unusually frigid weather was blamed for slipping output of natural gas in the United States on Thursday as California warned of short supplies and No. 2 U.S. producer Chesapeake Energy Corp said foul weather hurt its operations.
The comments from Chesapeake Chief Executive Doug Lawler came as spot prices for natural gas, widely used to fuel power plants, spiked to the highest levels since 2008.
Freezing temperatures across the country this winter have pushed demand to all-time highs and filled the pipeline system to capacity, and at the same time prompted a number of companies to say foul weather has snarled production.
The Independent System Operator in California issued a conservation alert saying "a shortage of natural gas triggered by extreme cold weather in much of the United States and Canada is impacting fuel supplies to Southern CA power plants and reducing electricity generation." California is facing a severe drought which could affect hydropower.
Estimated U.S. natural gas output is running about 0.8 billion cubic feet per day (bfcd) lower than the 30-day moving average and is off 1.5 bcfd from the start of this year when temperatures were more moderate, according to Thomson Reuters Analytics - which sees current U.S. pure dry gas production of 65.2 bcfd.
Bentek Energy, an energy analytics firm, said U.S. production fell to 64.5 bcfd on Thursday, down some 2.2 bcfd from normal levels because of freeze-offs. Cold weather can cause wells to malfunction and contribute to ice storms that make transport difficult. Bentek said basins in the Southeast and midcontinent were contributing to the most significant impacts, down 1.4 bcfd.
Chesapeake's average daily oil and gas output in December was well below its expectations due to "weather challenges" that continued into January and February, Lawler told analysts on a conference call on Thursday.
Fourth-quarter and first-quarter production will be affected by the icy conditions that hampered some of the company's operations, but output should "ramp up" on a sequential basis in the second quarter, Lawler said.
On Tuesday, Chuck Meloy, an executive at Anadarko Petroleum Corp, said on a conference call the company's operations in Colorado were finally returning to normal.
"The Wattenberg field has suffered through the floods and the polar vortex and I'm sure the locusts are coming," he joked. "But ... our production is coming back."
Gas for Friday delivery at Henry Hub, the benchmark supply point in Louisiana, traded as high as $9 per million British thermal units early Thursday, its highest level since August 2008, traders said.
Futures prices were up more than 1 percent on Thursday after rising more than 7 percent earlier in the day.
They pared gains when U.S. Energy Information Agency data showed an estimated natural gas draw through Jan. 31 of 262 billion cubic feet, lower than the 270 bcf forecasted by analysts.
In Israel, Noble Energy Inc said cold weather affected results in the fourth quarter, but in a different way than its peers.
A rare December snowstorm in Israel, where the company has begun supplying natural gas for heating and electricity generation, sharply boosted demand.
The jump artificially inflated the company's production compared with year-ago figures. The company also forecast first-quarter production that will effectively be below fourth-quarter numbers due to the temporary spike in Israeli demand.
Executives said they expect production to slowly increase this year, and told investors they do not expect a similar jump in sales this year.
"The first quarter is really right on track with where we expected and right on track to deliver the growth rate that we've laid out this year," Chief Executive Charles Davidson said on a conference call with investors.