grammaticality - Is it correct to say "The reason is because ..."?

In a statement like

The weeds have grown overnight. The reason is because it rained yesterday

Is "the reason is because" good grammar? Isn't it better to say

The weeds have grown overnight because it rained yesterday

The second form seems simpler and the words the reason is seem to add nothing to the sentence. Is there any technical reason to avoid the longer form?

Answer

"The reason is because..." is wrong; the other one is the one to go with.

That "the reason" is already explaining why, i.e. the reason, so putting also because will create a sort of redundancy.

See this article, which goes more in depth.