It's just one more sign of the devastating power of Hurricane-turned-Tropical-Storm Harvey. The National Weather Service has had to add two colors to the ones it uses to indicate rainfall levels on weather maps.

In a tweet sent Monday, the NWS explained that so much rain has fallen on Texas and Louisiana because of the storm, the previous map code didn't cover it. Water levels could reach 50 inches in some areas, the NWS reports.

#Harvey in perspective. So much rain has fallen, we've had to update the color charts on our graphics in order to effectively map it. pic.twitter.com/Su7x2K1uuz — NWS (@NWS) August 28, 2017

"The tremendous rainfall in Texas is literally and figuratively off the map," an NWS spokesman told CNET. "In the original map, the top interval for the observed rainfall (marked dark purple) was for amounts of 15 inches and greater, with no upper limit. With Harvey, the updated map is more specific in showing the graphical depiction of rainfall intervals, which aren't often observed at such high levels."

Dark purple now represents 15-20 inches. The new map also uses a plum color to show rainfall of 20-30 inches and a pinkish lavender to show rain greater than 30 inches. Yes, a grim use of Prince's famed "purple rain."

The new levels are shown on current maps of the areas around Houston worst hit by the storm. Flooding in the area isn't expected to peak until Wednesday or Thursday.

"Before the storm is gone, some parts of Houston and its suburbs could get as much as 50 inches of rain," the NWS reported, according to CBS News. "That would be the highest amount ever recorded in Texas."

First published Aug. 28, 11:16 a.m. PT.

Update, 12:59 p.m. PT: Adds a comment from the National Weather Service. Also clarifies that the NWS added two new colors, instead of just the one mentioned in an earlier version of this story.

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