Following Garg and Garg, atmospheric water vapour content or specific humidity W at is used along with sunshine duration to obtain a relation to estimate the global irradiation G using data for stations near sea level only of north and central India. The method is extended to find D, the diffuse irradiation. The resulting equations are G = G 0(0.394+0.364 n/N′−0.0035 W at) D = G 0(0.306+0.165 n/N′+0.0025 W at) where N′ is the maximum duration for which the Campbell-Stokes sunshine recorder is active and G 0 is the extraterrestrial irradiation. The deviations are compared to those obtained by Mani and Rangarajan using Hay's formulae for G and D and also to those obtained by Garg and Garg for G.