LOS ANGELES (BLOOMBERG) - Californians once greeted hot summers by blasting the air conditioners and filling the pool. No longer.

Battered by drought and heat waves that are straining the power grid, the Golden State is asking residents to make do with less water and electricity, just when they really want to use both. It's an uncomfortable new normal for a state that used to celebrate summer.

Power grid managers have sent urgent pleas on three of the past four days, begging residents to cut their electricity use to stave off blackouts. And these calls are becoming a standard part of the summer, as residents are forced to adapt their lifestyles to the changing climate.

"Customer conservation, honestly, is going to be the single biggest variable this summer between whether or not we're able to avoid rotating outages," said Mr Elliot Mainzer, chief executive officer of the California Independent System Operator, which runs most of the state's grid. He warned the situation could last for several years.

Meanwhile, Governor Gavin Newsom is asking the state to use 15 per cent less water, as reservoirs shrink. He urged Californians to return to conservation strategies they adopted during the state's last big drought, from 2011 through 2017.

While residential consumption in the state is 15 per cent below 2011 levels, he said people can't use water as freely as they did in the past.

"The sober reality is, here we are again," Mr Newsom said Thursday (July 8) while standing in front of the Lopez Lake reservoir in San Luis Obispo County, which was at 34 per cent of its capacity.

The drought across the US West is also exacerbating the electricity situation, with power generation from hydropower in California and the Pacific north-west set to fall 11 per cent this year.

The twin crises are deeply intertwined. Climate change has fuelled this summer's historic heat waves, scientists say, with Las Vegas, Portland, Seattle and Salt Lake City tying or breaking their all-time hottest temperatures, according to the US Weather Prediction Centre.

In California, the heat quickly melted the Sierra Nevada snow pack and a drought-parched landscape drank it up before it could flow into the state's largest reservoirs, leaving them lower than normal.

And now the massive Bootleg Fire in Oregon is threatening one of the main electric transmission lines connecting California to the Pacific north-west, forcing the state to import power from elsewhere.

California's fight against climate change, paradoxically, has also played a key role in tightening power supplies.

As the state switches to solar and wind power, so many traditional power plants have closed that electricity supplies grow strained at sunset. Large batteries are being plugged into the grid to compensate, but many won't be running until later this year.

Most of California remained under excessive heat warnings Monday with highs set to top 38 deg C through the evening, the National Weather Service said. Some cooling from the weekend's record highs is expected by Tuesday, but many heat warnings will remain.

"The heat is still blazing," said Mr Bob Oravec, a senior branch forecaster at the US Weather Prediction Centre. "Temperatures do moderate a little across parts of the West, starting as early as Tuesday, but it is still a hot summer."

The California Independent System Operator again called on consumers to cut their power use Monday afternoon and evening.

The biggest crunch typically runs from 4pm to 9pm local time. Those are some of the hottest hours of the day, as well as when solar power supplies start to fade.

Meanwhile, the Bootleg fire in Oregon, which has pinched off power supplies from the north-west into California, grew to almost 62,300ha Monday.

The blaze is one of 59 large fires burning across several states, from Montana to Arizona, the National Interagency Fire Centre said. With at least 863,000 acres ablaze, satellite photos show smoke covering much of the West.

Air quality alerts have been issued in a number of western states, including in Yellowstone National Park, because of wildfire smoke creating dangerous conditions for children, the elderly, and people with respiratory conditions.

California officials have credited consumer conservation with helping prevent outages this year, but it remains to be seen how well the tactic will work long-term.

"The more times you do it, the less effective it is going to be," said Mr Michael Wara, director of the climate and energy policy programme at Stanford University. The state, he said, needs the right incentives to get people to conserve when needed. "The way you get people to behave is you pay them for it or charge them less," Mr Wara said.

California's utilities have for years been slowly shifting most customers onto time-of-use rates, which charge higher prices when electricity demand peaks in the late afternoon and evening.

And state officials this year have been running television ads urging Californians to "power down" between 4pm and 9pm, hoping to make conservation during those hours a habit even when heat waves aren't straining supplies.

Mr Mainzer said there's a danger that issuing too many calls for emergency conservation so early in the season could lead to less consumer response later on. California typically sees its hottest weather in August and September, and last year's rolling blackouts - the first to strike the state since 2001 - hit in August.

"This is a potential for fatigue with consumers, like 'Why are we in this situation?'" Mr Mainzer said Friday. "It's a fair question."