( ( Heat ( and ( summer months ) ) ) ( ( ( ( activate and ) increase ) ( the biting ) ) . ) )
(ROOT (S (NP (NNP Heat) (CC and) (NN summer) (NNS months)) (VP (VBP activate) (CC and) (VBP increase) (NP (DT the) (NN biting))) (. .)))
Heat and summer months activate and increase the biting.
(ROOT (S (NP (NP (DT A) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN increase)) (PP (IN in) (NP (NN length)))) (VP (VBZ happens) (PP (TO to) (NP (NN metal) (NN railroad) (NNS tracks))) (PP (IN during) (NP (NP (DT the) (NN heat)) (PP (IN of) (NP (DT a) (NN summer) (NN day)))))) (. .)))