To Taper or not to taper…

I currently live in LA and am running NY in 3 weeks. I set out on my longest run today (20 miles), but the heat on the boardwalk had other plans and I ended up only getting in 13 before feeling completely dehydrated and overheated (was fueling and hydrating plenty I thought)

Now I’m stressing myself out because I’m not sure whether to taper until race day or go for 20 next weekend? My longest run of training was 18 at 5 weeks out but I’m nervous that that isn’t enough and I am underprepared…

Should I taper and do my planned 16 next weekend or go for 20 with only 2 weeks before the race?