Hot weather from April to June, including a heat wave that sent temperatures soaring above 100 degrees for four straight days, led to a five percent increase in operating revenues for the Tennessee Valley Authority this quarter. But officials at the federal utility said it still wasn’t enough to overcome the loss TVA suffered earlier in the year amid the mildest winter in decades combined with a sluggish economy. TVA reported a $290 million net loss in the first nine months of 2012. Last year the federal utility reported a $35 million loss during that same time period. The announcement came Friday with the release of TVA’s third quarter report.