NEW YORK ( TheStreet) -- Traders returning to work after a long Fourth of July weekend have been greeted by scorching temperatures across much of the Northeast, with the National Weather Service even advising that the early July heat wave could produce "a dangerous situation."An excessive heat advisory went into effect for a handful of Northeastern cities on Monday, and is expected to remain in place for several days as high humidity levels and triple digit temperatures blast the region. Highs in New York City were expected to range from 100 to 102 degrees on Tuesday, prompting the city to set up cooling stations offering refuge from the heat. Other major U.S. cities are also under siege from skyrocketing temperatures; Philadelphia, Washington and Baltimore are all under heat advisories, as are large areas of New Jersey and northern Virginia. The rash of higher-than-normal temperatures have prompted concerns of heat-related illnesses or even deaths, bringing back memories of a 1980 heat wave that killed more than 1,200 people along the East coast. The almost unbearable conditions have inhabitants of affected cities longing for a wave of storms to move through later this week and provide relief. But investors in the United States Natural Gas Fund ( UNG) are cheering news of the heat wave, and hoping the blistering temperatures hang around for a while. As a result of the heat wave moving through the eastern part of the country, air conditioners in the entire region are running at full blast. That translates into a spike in power demand, which in turn increases the need for natural gas-fueled power plants. UNG was surging on Tuesday, climbing more than 4.3% in late morning trading. UNG utilizes a futures-based strategy to offer investors exposure to natural gas prices; the fund's current holdings consist of August contracts. By investing primarily in near month futures contracts, UNG offers investors exposure to natural gas; the fund exhibits a near-perfect correlation with spot prices. But it also has the potential to incur a material "roll yield" when it sells expiring contracts and purchases longer-dated futures each month, a factor that has historically caused UNG to lag the hypothetical return on spot natural gas prices.