How Much Rain Do We Need to End the Drought

[Updated July 20 for a more frequently updated map from the Climate Prediction Center]

People have asked me several times this week, “how much rain do we need to end the drought?”

There is no easy way to answer this. The normal rainfall per week in Illinois is about an inch. So we need that inch per week just to keep from slipping farther behind. Taking it a step farther, that means you need well over an inch per week to start recovering from drought. Of course, no amount of rain at this point will undo the damage done to crops already.

There is one product, based on the Palmer Hydrological Drought Index, that attempts to answer this question from the Climate Prediction Center. However, I would treat it as an estimate. Even so, it gives you an idea of how far we have to go for a recovery. They estimate that we would have needed 9 to 15 inches of rain across much of Illinois to end the drought. That is a tall order. The wettest July on record for Illinois is 8.03 inches in 1958 and the wettest August on record was 6.91 inches in 1977.

Personally, I’m not sure it would take record-breaking rainfall. And I’m not sure we want 9 to 15 inches over the course of one or two months because that could lead to all kinds of other problems like flooding and heavy soil erosion.

Based on past droughts in Illinois, a month with rainfall 50 percent above normal (around 6 inches) followed by several months with near-normal rainfall would be capable of turning things around without the more serious consequences of heavy rainfall.

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4 thoughts on “How Much Rain Do We Need to End the Drought

  1. Thank you for the information. How much rain do we get on average across the entire U.S.? How about globally? With some areas of the world receiving too much rain, while some too little, just wondering if it’s also a supply and demand issue. Thanks

  2. Here is what the National Climatic Data Center said about US precipitation, “Precipitation averaged across the CONUS [continental US] in 2012 was 26.57 inches, which is 2.57 inches below the 20th century average. Precipitation totals in 2012 ranked as the 15th driest year on record.” As far as global precipitation, it tended to balance out – areas in drought are balanced by areas with too much precipitation. While we were dry, parts of Europe and Africa were wet.

  3. Thank you Jim for the information. It’s interesting (and good news) that global precipitation is fairly steady. It looks like the idea of fresh water import/export has been around for a while to take advantage of this, but never really implemented. Do you think, in theory, a global fresh water network is a good idea and might help “Mother Nature” with distribution?

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