The massive drought afflicting the western United States is getting worse.

Every part of California is now facing severe drought

Half of the mainland United States is facing drier-than-usual conditions, with 15 percent of the country experiencing "extreme" to "exceptional" drought. That in itself is far from unprecedented (it happened in 2012 and 2013, for starters) but it's a significant event.

The real problem, though, is in California, which is facing one of its worst dry spells on record — every single part of the state is now facing "severe" drought or worse. Dry conditions may be one reason why large wildfires are breaking out in California a few weeks earlier than usual. The drought is also hurting the state's crucial agricultural sector.

Droughts are hardly new in US history, and they've been a regular feature of the West for many, many years. But the current drought in California is serious even by historical standards. Here are five maps breaking the situation down:

1) Half the United States is facing drought conditions

Here's NASA's Earth Observatory: "As of May 6, 2014, half of the United States was experiencing some level of drought. Nearly 15 percent of the nation was gripped by extreme to exceptional drought. For the Plains and the Southwest, it's a pattern that has been persistent for much of the past several years."

Much of the US has been in drought since 2012

This isn't a one-year event: at least half of the United States has faced drought on and off since 2012 — at the peak in July 2013, some 81 percent of the country was experiencing at least some level of drought.*

Put together, the 2012-14 drought has been one of North America's biggest since the costly 1988-89 drought.

(Some quick background: A drought typically occurs when a region stays abnormally dry for a long enough period to cause an imbalance in the water cycle. Droughts are complex and can have multiple causes: maybe less rain is falling, or maybe evaporation is speeding up due to heat or winds, or maybe there's less water to begin with — say, due to less snowpack during the winter. See here for more definitions.)

2) And 100 percent of California is now in drought

But the situation is particularly dire in California, which is on track to suffer one of its worst droughts in at least 500 years. The country has been in drought all year, but conditions worsened this past week.

California is on track to suffer one of its worst droughts in 500 years

According to the US Drought Monitor, every single part of California is now facing "severe," "extreme," or "exceptional" drought — the first time that's happened in the monitor's 15-year history.

What happened? Much of the state was already in drought in 2012 and 2013, but conditions worsened considerably this year. A blocking ridge of high pressure kept California hot and dry during the normally wet winter. That means there was far less snow falling on the Sierra Nevada mountains — and hence less snow melt providing water during the spring.

That's bad news for California's agricultural sector, which is responsible for about half the fruits and vegetables grown in the United States. Mother Jones has an excellent set of maps showing how crucial California is for foods like almonds, broccoli, and grapes. And National Geographic has a look at several ways California is frantically trying to conserve water — like eliminating water-hungry lawns in Sacramento.

3) The West is facing a much higher risk of wildfires

National Interagency Fire Center

Thanks in part to the drought, the National Interagency Fire Center is currently predicting "above-normal" wildfire potential out in the western United States this summer.

That's already started in California — on Wednesday, a spate of wildfires broke out, burning more than 10,000 acres in San Diego County. These fires are breaking out a few weeks earlier in the year than usual. It's not clear what, exactly, caused the fires, but the fact that forests are dried out from a lack of water likely helped.

4) The US government is handing out disaster aid

USDA

The drought is affecting farmers and ranchers across the country. At least 54 percent of the US wheat crop has been hit by drought, 30 percent of the corn crop, and 48 percent of cattle.

Ultimately, the drought is going to cost taxpayers

That's expected to raise the price of some foods — including things like avocados and lettuce from California, as well as pork and beef.

And, as the map above shows, the US Department of Agriculture has declared a number of areas in the United States "disaster counties" whose farmers and ranchers are eligible for certain emergency loans.

Ultimately, the drought is likely to cost taxpayers — as crop insurance payouts soar and emergency aid programs kick in. Drought in 2011 cost some $11 billion in crop insurance payouts alone, estimates Taxpayers for Common Sense. Drought in 2012 then cost a record $14 billion. This year's drought could well top that still.

5) And the drought is expected to persist through summer

National Weather Service

The West probably can't expect much relief anytime soon. The National Weather Service is predicting that drought conditions will persist in the West and southern Plains regions all through the summer.

It's possible that next winter could be a different story. Right now, it's looking as if an El Niño is likely to form in the Pacific Ocean later this year — and, historically, El Niño events bring wetter winters to California. Still, this is far from certain, and it depends on the type of El Niño we get.

Further reading: For those interested in the connection between climate change and drought, here's an old piece I wrote surveying the science on the topic. It's not very clear whether global warming drove the drought in California (although hotter temperatures likely made the drought worse). But many climate models do predict more severe droughts in the Southwestern United States as the planet warms up.

* Update: Over at the Washington Post, Philip Bump put together some excellent graphics showing drought levels over the last decade.