Making sure that you're prepared for weather extremes is always a good idea! But as far as cold temperatures in NOLA, the data show that the number of really cold days has declined over time. This is a very back of the envelop breakdown of daily minimum temp (i.e., the overnight low) in New Orleans since 1893. The ups and downs are the seasonal changes, with summer temps at the peaks of the line and winter temps in the valleys.

I divided the whole thing into 4 equal blocks and counted the number of times the valleys touched or went below the freezing line and below the 20-degree line.

Seems clear that winters with nighttime temps below freezing have declined and winters with at least one night in the 20s have nearly disappeared. This pattern is consistent with long-term global warming, which for most places will gradually eat away at the coldest margins of that location's climate--nights will warm faster than days, e.g., and winters will warm faster than summers.

So, maybe extremely cold nights are becoming less common, so when they do still occur (and they do!) they stick out in your mind?