Biggest US grid operator issues emergency alert amid record-breaking heatwave

PJM Interconnection declared a level one emergency due to high electricity demand from heatwave.
Alert indicates PJM has resources to meet demand but is concerned about sustaining reserves.
Demand forecast to reach 153,286 MW while capacity is around 186,000 MW.
Hot weather alerts also issued earlier this week in anticipation of high demand.
Heatwave expected to make July the hottest month ever globally, straining grids.