G. Hermida-Nadal was born in Aguadilla, Puerto Rico in 1941 to Angel Hermida-Méndez and Teresa Nadal-Grau.
[2] Hermida obtained a Bachelor of Science in Physics (1963), cum laude from the University of Notre Dame with a General Motors National Scholarship.
He received a National Aeronautics and Space Administration Fellowship for graduate studies in Physics at Duke University from 1963 to 1964.
The next year he became Director of the Legal Division of Puerto Rico's Environmental Quality Board (Junta de Calidad Ambiental).
He then served as President of the Advertising Review Board of the State Elections Commission of Puerto Rico) and as Member of the “Blue Ribbon Committee” or the Independent Commission of Citizens to Evaluate Government Transactions (Comisión Independiente de Ciudadanos para Evaluar Transacciones Gubernamentales) established by the first elected female governor in the history of Puerto Rico Sila María Calderón.