(Reuters) - California's power grid passed its first test of the summer with no rolling blackouts on Monday, when customers cranked up their air conditioners as temperatures soared into the triple-digits for the second consecutive day in some southern parts of the state.

The California Independent System Operator, which manages the state's power grid, issued a so-called flex alert on Sunday, urging homes and businesses to conserve energy on Monday afternoon.

As consumers heeded that call and temperatures on Monday came in a little cooler than expected, the ISO cut its peak power demand projection for the day to 43,728 megawatts from 45,316 MW.

Monday's alert was the first big test of power generators' ability to meet heightened energy demands in the greater Los Angeles area without natural gas supplies normally furnished by the now-crippled Aliso Canyon. The storage field, California's largest, has been effectively idled since a major well rupture there last autumn.

So far, the ISO has not issued another flex alert for Tuesday but said on its website it would be "helpful" if customers conserve energy.

With cooler temperatures expected for the rest of the week, the ISO forecast demand would peak at 42,581 MW on Tuesday and just 39,036 on Wednesday.

AccuWeather meteorologists forecast the mercury would reach 87 degrees Fahrenheit (31 Celsius) in Los Angeles on Tuesday before falling to a near-normal 82 degrees on Wednesday. They had exceeded 100 degrees on Monday.

With Aliso Canyon shut down, state regulators have warned that the Los Angeles area faces up to 14 days of gas shortages severe enough to trigger blackouts this summer.

Aliso Canyon, owned by Sempra Energy's Southern California Gas Co unit, normally supplies the region's 17 gas-fired power plants, hospitals, refineries and other key parts of the state's economy.

(Reporting by Scott DiSavino; Editing by Lisa Von Ahn)