the final 3200 at runninglane was 72 degrees at 93% humidity which gives a dew point of 70.
From my experience it depends on the runner. Some runners bodies can't take the heat or humidity. Others won't be affected by it. Especially if we are talking about a 3200 which let's real is on the short side of racing.
For example, take Ben Anderson for example-
9:00 - Arcadia - Absolutely perfect conditions as always
9:15 - Colorado State Championships - 5500ft altitude
8:52 - Runninglane Nationals - 70 dew point - not ideal
9:04 - New Balance Nationals - Conditions were actually as good as Arcadia this year
For a 3200, it's a mixed bag.