Downwind Departures--JFK Yesterday 7/28

Yesterday I departed JFK around 4PM. They were operating 13's due to what appeared on the wind sock to be a strong wind from the S/SE.
As we taxied past the Port Authority PD building we stopped for about 10 minutes, turned LEFT and wound up departing 31L-into a significant tailwind....took off around 4:45.

Anyone have an idea why they would do downwind departures when the wind was rather strong in the opposite direction? I thought it might have something to do with the groundbreaking for the runway but I thought that was in the morning.

Thanks

To avoid thunderstorms possibly?

I thought so too but the climb out from 31L actually put us closer to the only cell in proximity, which was a little southwest of EWR at the time.

Just curious, how was the actual take off & climb ?