looking at the data very quickly and coming to a tentative conclusion, it may be less controversial to say that ottawa has the coldest winters of any capital city in the world (perhaps excluding the central asian ssrs, including mongolia). a cursory glance suggests that an ottawa january is 5-10 degrees colder, on average, than the baltic, north sea or iceland. but, these cities don't seem to get nearly as warm in the summer, for the same reason that they don't get very cold in the winter - the ocean currents regulate the climate. 

again: i'm not confident in data from bad sources when it defines itself poorly and then contradicts itself. i don't believe that the average temperature in ottawa is higher than the average temperature in helsinki. at all. that makes no sense. but, if the numbers are closer than meteorological science suggests they should be, it would be because the hotter summers in ottawa are warping them, which may be particularly evident since 1998.