Days of swelteringly hot weather followed by a thunderstorm warning caused the price of electricity to spike 1000% for New York City Monday afternoon.

The spot price of electricity was $94 per megawatt hour at 2:30 p.m. as the heat climbed over 90˚F. A reading from 3:30 p.m. -- shortly after a storm warning -- put the price at $1,042 per megawatt hour. The increase was reported earlier by Bloomberg News.

It won't necessarily affect New Yorkers' electricity bills. New York ISO, the organization that oversees the state's electric grid, works to keep overall energy prices relatively steady -- and spot prices reflect only a small portion of what drives those trends.

But with air conditioners on full blast to battle the afternoon heat, followed by the threat of lightning strikes taking out transmission lines or generators, the severe price hike on Monday afternoon highlights a broader problem with New York City's electricity market: Reliability.

Summers have grown increasingly warmer. The city's population continues to grow. And Manhattan and Long Island need new transmission lines to bring more power to the densely populated area. That makes it difficult for grid regulators to keep electricity -- and its prices -- flowing steadily when electricity demand peaks.

Power utility Con Edison has asked tens of thousands of customers to start conserving energy amid the extreme heat and equipment repairs.

The city can look forward to temperatures in the next few days with forecasts of thunderstorms by the end of the week.

Correction: A previous version of this story misidentified megawatt hours as kilowatt hours.