(Reuters) - California's power grid operator issued an alert urging consumers to conserve electricity on Wednesday as a heat wave baked the state, especially in the north.

Electricity supplies statewide are expected to be tight because of high summer temperatures driving up demand, power plant outages, and reductions in the capacity of transmission lines, the California Independent System Operator (ISO) said in a statement.

Power imports may also be limited Wednesday because of high temperatures in neighboring states, the ISO said.

Earlier Wednesday, the ISO told electric companies to restrict maintenance work on their generating facilities and transmission lines to help maintain reliability.

The ISO forecast that peak demand would reach 45,876 megawatts on Wednesday and 46,866 MW on Thursday. Though high, the levels would fall short of the 2015 peak of 47,358 MW in September and the grid's all-time record of 50,270 MW set in July 2006.

Restricting maintenance and issuing so-called flex alerts for conservation are among the first of many steps the ISO can take to help maintain reliability during times of high demand or other stresses.

AccuWeather forecast that temperatures in San Jose, the third biggest city in California, would reach 93 degrees Fahrenheit (34 Celsius) on Wednesday and 89 on Thursday after hitting 94 on Tuesday.

High temperatures in Los Angeles, meanwhile, were expected to remain at near-normal levels in the mid-80s for the rest of the week.

State agencies in April warned that millions of electric customers in Southern California could suffer power outages of up to 14 days this summer due to the limited availability of Southern California Gas' Aliso Canyon natural gas storage facility after it shut due to a closure massive methane leak.

SoCalGas, a unit of Sempra Energy, said it had enough gas to meet demand this week. The company said on its website it expects to deliver over 3.3 billion cubic feet (bcf) of the fuel on Wednesday and just under 3.3 bcf on Thursday, with almost 3.0 bcf coming from pipelines and 0.3 to 0.4 bcf from storage facilities.

If correct, the projected Wednesday delivery would be SoCalGas' biggest demand for the fuel so far this summer.

When the company last delivered 3.3 bcf on June 20, it warned customers that supplies could run short. The company however has not yet issued any similar warnings for Wednesday.

(Reporting by Scott DiSavino; Editing by Jeffrey Benkoe)