(Brian Brettschneider)

Having trouble wrapping your brain around the massive quantities of rain Hurricane Harvey's been dropping on the Houston area?

Here's one way to think about it: From 11 a.m. Friday through 11 a.m. Central time on Monday, Harvey dropped an average of 27 inches across the entirety of Harris County, Tex. That's more rain than most of the western half of the country has seen all year, according to climatologist Brian Brettschneider.

In the map above, every area in red has seen less than 27 inches of precipitation since Jan. 1. That includes all of North Dakota and Arizona, and just about every location in South Dakota, New Mexico, Colorado, Wyoming, Utah, Nevada and Montana.

Even a handful of locations in some of the wetter eastern states, like Virginia, North Carolina and New York, haven't hit 27 inches yet for the year.

For a slightly different way of looking at it, consider the map below of average annual precipitation.

(PRISM Climate Group, Oregon State University)

Harvey has dropped more rain on Harris County, Tex., in the past few days than the places on the map colored red through yellow receive in an entire typical year. Some places have seen 35 inches or more.

The snowhounds among us may want to consider it this way: According to the National Severe Storms Laboratory, one inch of rain is equivalent to about 13 inches of snow, although that can vary depending on local conditions. Accepting the 1-to-13 conversion, Houston's 35" of rain so far would work out to nearly 38 feet of snow -- well above the roof of a typical ranch-style home.

As of noon on Sunday, Harvey had dropped more than 9 trillion gallons of water on Southeast Texas, an amount visualized here by The Washington Post's Capital Weather Gang.

The final tally may be more than twice that much, at 21 trillion gallons or more — enough to fill Utah's Great Salt Lake four times over.

Alternatively, you can get a pretty good sense of the magnitude of the storm just by looking at a few photos.


A home is surrounded by floodwaters from Tropical Storm Harvey in Spring, Tex. (David J. Phillip/AP)

Rescue boats fill a street as flood victims are evacuated in Houston. (David J. Phillip/AP)

People view the flooded highways in Houston. (Thomas B. Shea/AFP/Getty Images)

Widespread flooding from Tropical Storm Harvey is seen in La Grange, Tex. (Ralph Barrera/Austin American-Statesman/AP)