Your sentence is grammatical and makes good sense. To improve it, use a verb to expresses your main thought. As is, the only verb you use is "has". It is a verb that doesn't say anything. The idea you are trying to convey is that the quantity of rain is somehow "too much". Why is it too much? What effect does it have on you that makes you feel that it is "too much". What does it do to you? Does it exhaust you? Does it bore you? Does it irritate you? I can't tell you what the correct answer is. Only you know. Decide what it does to you and use that to choose your verb accordingly. For example, you could write: "The intermittent and never ending rain today bores me so."