*4.2.2 Sub-periods (30 year non-overlapping)*

Values of the student's *t*-test show a significant deviation in trend from the sub-period, 1961–1990 to the sub-period, 1991–2020 (**Table 4**). These values show a significant deviation and shift towards a positive and increasing trend in the series of Yelwa, Sokoto, and Kaduna. For these stations/sub-areas, the sub-period of 1991–2020 appears to be wetter than the preceding sub-period of 1961–1990.

## **4.3 The trend in temperature of study area**
