We report on our ongoing project "Statistical studies of HII regions in the nearby extragalaxies". In EWASS 2014 we presented the overview of our detailed study of warm dust in the nearby Galaxy NGC 4321 (M100), which included new relations between the Halpha luminosity and the near-IR luminosity and temperature of some 275 HII regions in M100. In the present report, we show our new measurements the flux values in the 4 Spitzer-IRAC bands of a complete sample of 70 isolated luminous HII regions in NGC 4736 and 157 regions in NGC 4254. We estimate the near-IR luminosities and compare them with the Halpha luminosities from the literature. We can now compare the results obtained from these three galaxies. We find a linear relation between the Halpha luminosity and the Spitzer IRAC luminosity in the near IR for the HII regions, but no apparent relation between the luminosity and the colour temperature of the regions in M00, and now in NGC 4736 and NGC 4254. The colour temperatures of regions, notably in M100 and in NGC 4254 are confined to a surprisingly narrow range, with only a small fraction forming a higher temperature tail to the distribution. These results give new insight into the size function and the 3D distribution of the dust in these regions, and we propose scenarios to explain them.