The operators of the California electric grid, under a state of emergency since June, made it through the year’s first fierce heat wave, but face a near-perfect storm of setbacks as they struggle to keep the lights on until fall brings cooler weather. Be glad you don’t work there. Here is a brief list of what they’re facing:

The endless drought has so depleted the state’s reservoirs that only 20% of the normal supply of hydro power is available. Hydro is one of the largest sources of California’s power.

The largest source of electricity in the southern half of the state, natural gas, is not available at all due to the shutdown of the massive storage facilities in Aliso Canyon after they leaked massive quantities of natural gas into the atmosphere — for four months.

The summer heat, and the electricity needed to deal with it, are both seeking new record highs this year.

With the system thus stretched to its utmost, natural disasters also threaten. Wildfires, which are breaking out earlier in the year, getting bigger, and lasting longer than ever, not only damage the grid directly, but their smoke ionizes the air and bleeds power from transmission lines and force operators to reduce line voltages.

And then there’s the really big gorilla in the room, the Big One, earthquake that is, that will destroy much of the California grid, and that’s not all.

To understand how frail this all is, keep in mind the following:

There must be present on the grid, at all times, exactly enough electricity to match demand. Fall a little short and you have a brownout that can seriously damage electric motors and electronics. A little too much and circuit breakers start tripping to contain the surge, a process that can very quickly get out of hand.

There are massive generators running all the time whose output is mostly not used, but must be available instantly to meet additional demand. The operators calculate the expected peak demand, add a margin of safety, and keep that much current available. If it were not necessary to provide for peak demand, electricity cost would be cut in half.

Electricity travels at the speed of light. The system has to be tuned instantaneously. There is no margin for error.

If, despite all precautions, demand for electricity exceeds the supply available on the grid, operators shut off power to sections of the grid to prevent the whole thing from going down. To spread the burden, after a while they restore power to the section and shut down another one for a while. This is called a rolling blackout. The California Independent System Operator has warned its customers in Southern California not only to expect rolling blackouts (they have become a feature of every summer) but that every customer should expect to be without power for a total of 14 days this summer.

Those are the planned outages. There have been 470 unplanned outages so far this year in California, caused by the usual suspects: falling tree branches, lightning strikes, and “I told you not to touch that.”

Should one of the stressors get out of hand, or one of the defenses not work well enough, Californians will not be the only ones to suffer. The tremors in the Midwest System Operator’s grid first noticed in the early afternoon of August 14, 2003, within hours turned into a tsunami of runaway power that blacked out New York City, eight American states and two Canadian provinces for up to two days.

With the temperatures rising, the water evaporating, the fires raging and the earthquake coming, think of the California grid as a guitar being tuned a too high. First you just get higher and higher notes. Then there’s that awful snap.