Your requirement is not clear to me. The semantic content of both lines is the same (Temp: 37.8°F), the rest is just HTML fomatting. Why can you skip the first line but not the second? Schouldn't you look for a way to ignore the <span>-Tag only instead of the whole line? Also I'd recommend a framework for parsing HTML because there may be line breaks that split your line and you may not find it.
Having sad this a look ahead expression may do it: