No, there was weather for all flights.
AAL120 was scheduled to depart at 2110EDT or 0110z.
Here's the weather just prior to departure;
JFK Airport
METAR‏@metar_kjfk
KJFK 190055Z 22016KT 2SM R04R/5000VP6000FT TSRA BR FEW008 BKN013 OVC020CB 20/19 A2970 RMK AO2 TSB54 OCNL LTGICCC OHD TS OHD MOV NE P0003
If you're not familar with the abbreviations involved it indicates that at 0055z on the 19th (190055z) or 8:55pm on the 18th the winds
were out of the southsouthwest at 16 knots (18 mph) (22016KT). The visibility was 2 statute miles (2SM) but on runway 4 right
visibility was as low as 5000 feet. (slightly less than a mile) (R04R/5000VP6000FT). The thunderstorm was overhead (OHD) moving to the NE (MOV NE).
Because JFK was using only one runway (22R) for departure, published delay reports by the FAA showed 90 minute delays during
that time. But because the thunderstorm was moving east of JFK it blocked departure paths to the east after that time, increasing delays for European bound flights to over 2 hours in some cases. Westbound flights didn't experience delays as long during that time,