<b>The Impact of Temperature and Relative Humidity Elevation on Mental Health of In Patient Admitted Into Jos Teaching Hospital Jos, Plateau State, Nigeria</b> The paper examined the impact of temperature and relative humidity escalation on mental health of in patient admitted into Jos Teaching Hospital JUTH Jos, Plateau State, Nigeria. The main independent variables of interest were temperature and relative humidity we also employed two derived parameters heat index and overlapping effect in our analysis in which we used four years 2011 2014 data of psychiatric cases and in patient that were admitted in the hospital, ex post facto research design was adopted for the study. The population of the study comprised 2073 in patient that was admitted in the hospital from the year 2011 2014 was sample used for the study. Data collected were analyzed with used of single regression and multiple regression analysis with complex heat index formula. The study found climate parameters temperature and relative humidity and their counterpart derived parameters heat index and overlapping effect make population vulnerable to the risk of psychiatric cases and do increase the numbers of patient admitted in the JUTH. There were positive association between the numbers of in patient in the JUTH and those parameters with 41 and 38 critical acute psychiatric cases due to overlapping and heat index effect respectively. In other word 79 10.2 of the total 778 numbers of patient traceable to those parameters were in critical acute psychiatric condition. Increase in the relative humidity and overlapping made population more vulnerable to the risk of psychiatric cases with approximately equal strength than the heat index and temperature. But the heat index makes more risk than temperature. The vulnerability of population to psychiatric cases was not equally distributed throughout the year 2011 2014. Population response differently to the impact of each parameter throughout those years considered. The effective strength of relative humidity determines the effective strength of the overlapping effect and the effective strength of temperature determine that of the heat index. Temperature, Relative Humidity, In patient and psychiatric cases 125-136 Issue-2 Volume-4 Jaiyeola O. Paul | Abdullahi Ayegba | Abimaje Okolo Suleiman