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Using the $IRAS$ Sky Survey Atlas, we have investigated the spatial and temperature structure of the the local interstellar medium in the northern half of the first and second quadrants of the Galaxy ($10^{\circ} \leq b \leq 50^{\circ}$ \& $42^{\circ} \leq l \leq 146^{\circ}). The ratio of I$_{60\mu\rm{m}}$ vs I$_{100\mu\rm{m}}$ is found to be 0.1735 ($\pm$0.0004) indicating an average dust temperature of 24K impling that the 60$\mu\rm{m}$ and 100$\mu\rm{m}$ intensities are primarily produced by the thermal emission of large dust grains in thermal equilibrium with the interstellar radiation field.
In addition, we have found a significant longitudinal dependence for the temperature associated with the interstellar dust. Using 1$^{\circ}$ wide longitude bins, we find the average dust temperature varies by more than 20\% with a general gradient of decreasing temperature with increasing longitude. Further we find that the total surface brightness, in the same longitude bins, is anti-correlated with the temperature indicating that the hotter dust is associated with regions of lower dust quantity.
