1) The blessings on lightning and thunder are made with Hashem’s Name and His Kingship. (This means that we say the entire blessing like any other.) However, the halachic authorities (Ben Ish Chai and Kaf Hachaim) write that the Sephardic custom is to make these blessings without Hashem’s Name and His Kingship.
2) One who hears thunder or sees lightning, even if he is unsure if his hands are clean, is allowed to assume that they are clean and he can therefore make the relevant blessing without washing his hands. If a person has come out of the bathroom with clean hands when he still needs to wash his hands because of the evil spirit which rests on the hands, seeing that if he would wait until he washes his hands he will miss being able to say the blessing, he should make the blessing without washing his hands (Mishne Berurah 227,11). Some say that in the Zohar it is apparent that one should not make the blessing without washing one’s hands even if by washing one will miss saying the blessing. (Kaf Hachaim ibid)