January is usually San Francisco's wettest month, averaging four and a half inches of rain since 1850. In January 2015, though, it hasn't rained at all -- and the forecast doesn't suggest that's likely to change. Over the past 165 years, that has never happened. Not once. The closest the city came to a rainless month was when it got 0.06 inches -- in 2014.

The current problem, as you know, is the persistent drought in the state, which, thanks in part to heavy rains in December, has actually eased slightly from its worst point. Slightly. According to data from the National Drought Mitigation Center, the current state of drought in California is still like nothing seen this century.

Or, to put it another way:

That darkest red part -- the part that's so prevalent in 2014 -- is the measurement of "exceptional drought."

Research suggests that the drought is a function of a warm patch in the Pacific Ocean, which has prevented precipitation from reaching the state. Record heat in the state (it and Nevada and Arizona saw their hottest years on record in 2014) has made a bad problem worse.

The Senate has been debating a bill aimed at providing assistance to those affected by the drought, so far without result. Of course, the Senate also spent much of the week debating the existence of climate change, which scientists say will likely lead to more expansive, more prolonged droughts in the Southwest. That would mean more droughts like this one, with more future debates over how to help those affected (even as, we would stress, the cause of this drought doesn't appear to be the warming climate).

In opposition to the week's climate change amendments, Sen. Jim Inhofe (R-Okla.) argued that it was vain for humans to think they can change the weather, referring to the scientific evidence that emission of greenhouse gases is responsible for the warming climate. The California drought offers a good sense of the scale of the problem -- and, to rework Inhofe's idea a little -- the challenge that reversing climate change presents.