Why does relative humidity seem to correlate with high temperature (at least where I live)? I live in New Jersey.  Now that summer is coming on us, temperatures and outdoor relative humidity are both increasing.  I've noticed the few years that I've lived here that there seems to be a rough correlation with a day's high temperature and the relative humidity.  I've always found this odd, since for a fixed amount of moisture in the air, relative humidity will go down with increasing air temperature.  However, the hottest days (as the thermometer reads, not just as I feel) also seem to have the highest relative humidity.

I lived in Hong Kong for two years and the same thing seemed to happen there.  The hottest days also had the highest humidity (and were usually accompanied with the formation of a typhoon).

What makes relative humidity go up with hotter days?
In coastal New Jersey, relative humidity is maximal in the early fall when the ocean temperature is warmest, and minimal in early spring when the ocean is coldest.  However, the monthly variation is rather small:  

Atlantic City, New Jersey:  

70 January
69 February
67 March
66 April
71 May
73 June
74 July
76 August
76 September
75 October
73 November
71 December
72 Annual 

Newark, New Jersey  

65 January
63 February
60 March
58 April
62 May
63 June
63 July
66 August
68 September
66 October
67 November
67 December
64 Annual 

source: https://www.currentresults.com/Weather/New-Jersey/humidity-by-month.php