significantly different from long-term?

[scoter]

I have daily temperature readings over a given time period (say, May 1 to May 15) for 7 years. I want to know if this period (call it early May) was hotter or colder than the long-term average for any of the years of my study (e.g., in 1997, early May was significantly hotter than the long-term average).

For the long-term temperatures I have the mean and standard deviation from 30 years of measurements (e.g., mean and SD for May 1st, mean and sd for May 2nd,...)

I thought this would be easy but I'm stumped. I hope someone can enlighten me.

thanks for any input!