During the July 4 weekend, a heat wave pushes the power grid in Virginia close to its limits, leading a major data center to rely on backup power. According to reports, dark smoke was seen rising above a Digital Realty facility in Ashburn, the result of operations involving diesel generators. The company activates the generators as demand for electricity increases and grid capacity becomes constrained during the unusually hot weather. The incidents highlight how extreme temperatures can affect power availability for large electricity-consuming sites such as data centers and can require switching to emergency generation when utilities cannot reliably supply the needed load. The reports describe the event in terms of grid strain and the use of backup generators rather than a specific technical failure. While the smoke is visually notable, it is linked in the coverage to generator operation during the peak heat period.