Variation in pronunciation of the French nasal vowels among French dialects?

Standard French is Parisian or so. Temps and Clan have the same nasal vowel, nasal a (which I don't have on my keyboard), and possessive Ton and Son have the same nasal o. Southern French has a special way of pronouncing nasal vowels, but I don't think you have to bother. You'll adapt to that special accent easily. The thing is that in some areas the nasal consonant is faintly audible.