ENERGY CRISIS HINGES ON CLIMATE.

MOST summers, Angelenos give little thought to the weather. And why should they? The sun comes up, thermometers rise, air conditioners go on and people flock to the beach or to air-conditioned malls. A real yawner.

Not this year. The weather is looming as the single biggest factor in summer plans for local businesses and residents. For every degree that the mercury rises, the risk of those dreaded rolling blackouts increases. And so does the risk of further electricity rate hikes. All of which could tip an economy in the midst of a slowdown into a full recession.

"The weather is absolutely the key to our ability to get through the summer," said Jim McIntosh, director of grid operations for the California Independent System Operator. It's McIntosh's responsibility to round up enough electricity for power-starved Californians every day to prevent rolling blackouts.

If California experiences a hotter-than-average summer, energy forecasters say residents and businesses could face up to 200 hours of rolling blackouts. If it's cooler than average, they might only see 10 to 20 powerless hours. The latter scenario would undoubtedly prompt many to say that the whole crisis has been overblown.

The last time Angelenos paid close attention to the summer weather -- during the 1984 Olympic Games -- the cooler scenario prevailed, which proved a blessing for athletes and fans alike. But hotter-than-average weather that summer would only have posed a mild inconvenience, not the economic damage it could wreak this summer.

It's not just blackouts and resulting loss of business that's at stake. State taxpayers and electricity ratepayers could be on the hook for hundreds of millions or even billions of additional dollars if hot weather drives up the spot market price of electricity.

"If you get a heat wave, power prices will rocket back up," said Michael Denton, vice president of strategic consulting for New York-based Caminus Corp., which sells risk management and trading software to the energy industry.

That, in turn, would force the state to spend more money on buying electricity, ultimately driving up the payback amounts for the $13 billion bond package that the state is readying to take to Wall Street.

And on the demand side of the power equation, don't expect consumers to dramatically curtail usage if the mercury rises to sweat-inducing levels.

"In the summertime, our load increases by about one-third, or 10,000 megawatts. Almost all of that is due to air conditioner use as temperatures rise," said Edison spokesman Gil Alexander.

Complexity of forecasting

With so much riding on the weather this summer, coming up with accurate weather forecasts is essential for the state's power grid operators. McIntosh and his team are constantly scrutinizing weather data and forecasts from Edmond, Okla.-based WeatherBank Inc. -- running it through their computers to come up with the daily supply and demand curves for electricity.

McIntosh said June was close to 30-year historical average temperatures in Southern California. For Northern California, the first half of the month was above normal, the second half slightly below.

For the next 90 days, the consensus is for temperatures to be above 30-year historical averages statewide. In its periodic bulletin, the National Weather Service predicts a 20 percent chance that temperatures will be "significantly above normal" for the state, compared with a 10 percent chance that temperatures will be below normal. The Weather Service does not specify how many degrees above normal the temperatures will be.

WeatherBank's California forecast calls for temperatures to be 1 degree to 2 degrees warmer than normal (30-year historical average) through the rest of the year, including the summer months. The only exception is the far northern coastal portion of the state, where WeatherBank expects to see about normal temperatures.

"Other models we've looked at 'seem to be in line with ours for the summer months, so I guess that's a consensus," said WeatherBank chief financial officer Michael Root.

Still, there are a lot of variables in forecasting the weather. That's why it's so hard to predict energy demand -- and with it, the prospects of rolling blackouts.

Here are just some of the weather factors that power grid operators keep tabs on:

* Higher-than-average temperatures in both the northern and southern portions of the state. Early last month, while Northern California and the Central Valley were sweltering with triple-digit temperatures, Southern California remained at or near average, which "made a tremendous difference in overall demand load for the state," McIntosh said.

* The proximity of ocean cloud or fog banks to the shoreline. "When the fog is just a mile or two off the Southern California coast, we're OK," McIntosh said. "It's when an offshore breeze pushes that fog bank back to, say, Catalina Island, that we know we're in trouble. If that happens in both Northern and Southern California, it can add 2,000 more megawatts of demand."

* The timing of heat waves. Most heat waves in California last three or four days. If a heat wave starts building on a Thursday or Friday, it typically peaks on a weekend, when many businesses are shut down. It's when a heat wave starts on a Sunday afternoon or Monday and builds through the workweek that the greatest chance of blackouts occurs.

* Higher-than-average temperatures in major Western U.S. cities. California imports anywhere from 10 percent to 20 percent of its total electricity supply, mostly in the form of hydroelectric power. "If it's hot in Seattle, Portland, San Francisco and L.A., then we're really in trouble, because Seattle or Portland won't have any extra electricity to ship to us," Mcintosh said.

* Rain levels in the Pacific Northwest. With that region experiencing a severe drought, water levels in dams on the Columbia River and elsewhere are at their lowest levels in decades. These dams aren't producing enough power for local residents, let alone for shipping to California. The supply squeeze would only worsen if the storm track continues veering north of Washington and Oregon.

Of course, there are other factors that come into play in determining the frequency of blackouts: the level of consumer conservation, the number of power plants that are on line, the availability of alternative sources of energy, like wind and geothermal plants, to name a few.

And in recent weeks, favorable developments in each of these areas have caused the crisis to ease somewhat.

Hopeful signs

Energy consumption statewide in May was down 11 percent from the like year-ago period, besting forecasts that it would be down only 7 percent. New power plants have come on line and other plants that had been down for "routine maintenance" during the winter months are now back on line -- whether because of legitimate repairs being made or more serious scrutiny by regulators to prevent market manipulation has yet to become clear.

All these factors give California power grid operators a little breathing room in their daily scrambles for power -- and maybe a little more room to withstand the vagaries of this summer's weather.

But all of this progress could be for naught if California and surrounding states go through a severe seven-to-10-day heat wave, or if onshore breezes that typically keep beach communities cool consistently fail to materialize.

"People in California are realizing just how much at the mercy of the weather they really are," said Michael Root, chief financial officer for WeatherBank.