The summer of 2014, overall, was fairly mild in New York City. We only had 8 days reach 90°F or higher. On average, the city typically gets 15. That said, this was just one season. Looking at long-term trends, the number of 90°F days in the Big Apple has actually been increasing.
The graph below shows the number of 90-degree days recorded in Central Park by the National Weather Service every year from 1870 to 2013. While there has been variability over the years, the trend is clearly on the rise.
To date, the most 90°F days that NYC has ever had in one year was 39. That happened in both 1991 and 1993. On the opposite end of the spectrum, 1902 only had one day hit the 90° mark. Last summer, we made it to 90°F or higher 17 times.