Hi Sultan, you may want to ...

Hi Sultan, you may want to determine if any similarities in rainfall amount is due to proximity or due to differences in elevation (as Horvath has suggested). It appears that gauge 3 is nearer to the base of the hills/mountains and, depending on prevailing wind direction, may experience higher precipitation. If there are more stations in the region, consider applying statistical model like the generalized additive model (R is an option to implement GAM), and inputting elevation, distance to coast, wind direction, etc. Then use results from GAM to predict rainfall between and around the stations. This is not an easy solution because rain is event driven, so you would need data going back a number of years. A Thiessen model may not be appropriate with just 3 stations - while it is theoretically possible to estimate between gauges, extrapolating beyond the gauges would lead to unsubstantiated values.