import csv

coldestYear = ''
coldestMonth = ''
coldestValue = 10000.0
months = ['jan','feb','mar','apr','may','jun','jul','aug','sep','oct','nov','dec']

with open("temperatures.csv", mode='r') as csvfile:
    reader = csv.DictReader(csvfile)
    for temps in reader:
        for month in months:
            if temps[month] != '' and float(temps[month]) < coldestValue:
                coldestValue = float(temps[month])
                coldestYear = temps['year']
                coldestMonth = month

print("The coldest month was {0} {1}, with a temperature of {2}.".format(coldestMonth, coldestYear, coldestValue))