Farmers like rain, but they don’t like the rain. What does this mean? All farmers like rain as it is good for their crops. If it doesn’t rain, their crops will die and they will have difficulty earning a living. Due to the nature of their work farmers like rain in and of itself. It would be quite unusual to find a farmer who doesn’t like rain.
However, there many be things that are associated with rain; such as getting wet, mud, not being able to go out, botched plans, etc., that a farmer might not like. When referring to the things that are associated with rain, the definite article is used…i.e. the rain. When the definite article is used with the word ‘rain’ it becomes an object activity noun.
Just to recap: Farmers like rain (rain in and of itself), but they don’t like the rain (the things associated with rain).