Please explain the heat island effect which leads to unusual raining in the area during non-monsoon period.
A heat island is a place with unussual high temperatures i relation with the surrounding landscape, depending on the scale, a city is a heat island in comparison with the (surrounding) natural habitat. however, inside cities, there are specific points with very high temps that could be identifyed. This can apply to country-side landscapes, where clear-cut pastures could achieve higher temps than cose forests or even shrublands. This "heat island effect" of course is variable in time, and will depend on the season, mainly becouse of incident radiation.
Heat island effect means warmer temperature in inhabited urban areas than surrounding nearby areas. And temperature is nearly 1- 12 0C higher is reported in areas affected by heat island effect. In smaller cities, heat island effect is not so distinctively visible , while in metropolitan cities, heat island effect is very much pronounced. There are three types of heat islands viz., boundary layer, surface later, subsurface later, the intensity and timing of these vary greatly but all three types of heat islands are harmful to human population...
For example, rooftops are usually black, that means they attract the sun and the air above them gets warmer. The same for road surfaces.
Compared to surrounding farmland, or grass land or forest, the city has more heat-absorbing surfaces, therefore, it is like an island of "hotter air".