Resample timeseries with maximum values

I've got 9 timeseries from a sensor, on a one second time interval. I need to resample each one of those timeseries to a thirty second interval, but instead of a linear interpolation, I need the maximum value for that thirty second interval, based on the data in the original timeseries. I wan't to avoid having to loop through all data to achieve this, but up until now I can't find another solution. Any ideas?