import csv

hottestYear = ''
hottestValue = -10000.0

with open("temperatures.csv", mode='r') as csvfile:
    reader = csv.DictReader(csvfile)
    for temps in reader:
        if float(temps['sum']) > hottestValue:
            hottestValue = float(temps['sum'])
            hottestYear = temps['year']

print("The hottest Summer was {0}, with a temperature of {1}.".format(hottestYear, hottestValue))