A couple of people have asked this question before, but I still do not understand.

Question

Highest/Lowest elevation for Long Beach = 360 feet and -7 feet

Highest/Lowest elevation for New Orleans = 25 feet and -8 feet

One of the cities has an average elevation of about 2 feet below sea level. Which city is it?

Answer 1

LB: (360-7)/2
NO: (25-8)/2

Even without doing the actual math, just seeing that much of LB is quite high should make things clear.

Now, neither of those averages is -2, but surely NO has a better chance of being near that.

What that means is that while the mean of high and low for NO is 8.5, if there is a lot more land below sea level than above, the average could be -2.