The last time we had a heat wave that lasted that long was 11 years ago. In August of 2002 we had a 9 day heat wave with temperatures of 90 degrees or higher from August 11th through August 19th.
An official heat wave here in New England occurs when we reach 90 degrees or higher for three or more days in a row. On average we get about two to four heat waves a summer. Most of them tend to last about 3 to 4 days but some have been longer.
In July of 2010 we had a 6 day heat wave from July 4th through July 9th and back in 1999 we had a 6 day heat wave from July 28th through August 1st.