This is Martinique, not Maine. Does the fog "roll in" like that at night? And what's with all the jacket-wearing? They're only in the middle of the freakin' Caribbean!
I asked the doctor to take your picture so I can look at you from inside as well.
The fog doesn't have to be in any way typical. It only has to be possible that there could be a relative cool snap of weather for a couple days that could generate fog (which will happen if the air is cooler than the water temperature). I doubt that people in Martinique go their whole lives without ever seeing fog.
As for the jackets: Haven't you ever noticed that people who have lived in hot climates for a while tend to grab jackets / coats at temperatures warm enough to make Northerners laugh? (In other words, it's consistent with the *relatively* cool weather front that would create the fog.) And on a damp night the French couple is wearing the type of rain coats (trench coats) that a French person at the time would be likely to own; probably warmer than they would need, but better than gradually getting soaked in the mist.
If by "jackets" you were referring to the "sport coats" / "suit jackets" that all of the men were wearing ..... That was just how people dressed then; much like women then were much more likely to wear skirts / dresses (compared to now), so too did men wear jackets and hats just as a matter of course when going out.
You've gotta keep in mind the era this was filmed in. In 1944, people didn't walk around in bikini's, swim suits, shorts, and tank tops like they do today. It was just a more formal type of dress, that's all.
Yes, I agree that generally the Caribbean is going to be too warm for wearing coats & jackets, but it does get pleasantly cool at night, especially if you are up at any altitude (like the Blue Mountains in Jamaica, for example).
Just chalk it up to use of cinematic license to adjust the clothing to fit what society expected back then.
Actually Martinique has a fairly moderate temperature of high 70's to high 80's. The west side of the island is on the Caribean, but the east side is on the North Atlantic, and the temperature is moderated by tradewinds.
Decades ago, I spent 13 months on an island not so far north of Martinique. The temperature was almost always around a hundred in the day time, except for a couple of months in the middle of the winter, when it was typically in the 80's. The temperature would fall suddenly after sundown from the hundreds to the low eighties/high seventies, and with the prevailing sea breeze it seemed quite cool. Sweaters and light sports coats were always comfortable at night.
He maketh His sun to rise on the evil and on the good... St. Matthew 5:45
Having sailed in the area, Martinique for sure has fog; and there are more than a couple ritzy French joints you could wear a suit to when the sun gets sleepy.