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An exclusive systematic study of the giant dipole resonance (GDR) parameters has been performed in very light mass nucleus P31 in the temperature range of ∼0.8–2.1MeV and average angular momentum of ∼11–16ħ. The high-energy γ rays from the decay of the GDR, evaporated neutrons and γ-ray multiplicities have been measured. The angular distribution of high-energy γ rays has also been measured at Ebeam=42MeV. The GDR parameters, nuclear level density parameter and nuclear temperature were precisely determined by simultaneous statistical model analysis of high-energy γ ray and evaporated neutron spectra. It is observed that the measured width remains roughly constant up to a temperature of ∼1.6MeV. Moreover, the thermal pairing plays no role in describing the GDR width in this open-shell light nucleus at the above-mentioned temperatures and angular momenta. The present measurements provide an excellent platform to extend the applicability of the existing theoretical models down to the very light mass nuclei. Keywords: Isovector giant dipole resonance, Statistical theory of nucleus, BaF2 detectors