Washington’s Fourth of July parade fell victim to a dangerous heat wave that gripped the nation’s capital on the country’s 250th birthday, forcing organizers to call off America’s Independence Day Parade before its Saturday morning start. The mayor’s office announced the cancellation of the 10:30 a.m. event, which organizers scrapped after the National Weather Service posted an Extreme Heat Warning for the District. Heat index values were forecast to climb between 110 and 115 degrees. Organizers said the safety of participants, spectators and staff drove the decision.Forecasters expected the temperature to peak near 102 degrees Saturday, according to the New York Post. That reading would beat the hottest Fourth of July on record in the capital, 100 degrees set in 1919. By midday, the city