U.S. Climate | April and May 2018

Two contrasting headlines about recent climate in the U.S. this spring caught my attention. Both came from NOAA’s National Centers for Environmental Information. The headlines were from the assessments of climate in the U.S. for April and May of 2018.

The contiguous United States had its coldest April in more than 20 years.

The contiguous United States had its warmest May on record.


The part of the U.S. where you live might not have seemed unusual. However, we noticed these differences in the midwest. Before examining April and May specifically, we will look at the climate for the year-to-date in the next two graphics. Relative to the period from 1895-2018, the upper plains was below average in temperature for the first five months of the year. The west was above to much above normal with record setting temperatures in the southwest.

Not shown in the graphic, the Alaska year-to-date temperature was 20.7°F, or 4.9°F above average. It was the ninth warmest on record. Western and northern Alaska were much above normal. Record low amounts of sea ice in the Arctic likely contributed to the warming.

The eastern U.S. was wetter than average year-to-date. Pennsylvania, New Jersey, Rhode Island and West Virginia had top ten precipitation amounts. It was also true for parts of the Northern Rockies and Plains due mainly to snow early in 2018. Below average precipitation was recorded in the Southwest, Great Plains and Upper Midwest. Some areas were much below normals.

April 2018 Assessment

The full assessment report for April can be found here. Parts of it will be highlighted in this post. April was the 13th coldest on record for the contiguous states. It was the coldest since 1997. Several anomalies are noted in the following graphic. Regions had record cold, heat, rainfall, snowfall, precipitation, and drought. It was a wide ranging mix of conditions. Click to embiggen to see the details.

The eastern two thirds of the country was cold compared to the period from 1895-2018. The upper midwest was especially cold, setting records. We in Iowa thought winter was never going to end. It was our coldest April on record. We had several snowfalls. The southwest region on the other hand had record warmth.

Large parts of the country received above average precipitation seen here in green. The southwest, Texas, and through the central states was dry. I mentioned above that Iowa had several snowfalls in April. Southeast Iowa shows record dry conditions for April. Our snows were very dry with high snow to water ratios. Concern is growing in the heart of the country about the drought conditions.

May 2018 Assessment

The full assessment report for May can be found here. As with April, several anomalies are noted in the following graphic. Click to embiggen.

Record warmth for the May was set in the northwest and in a large swath across the central part of the country. Most of the rest of the country was much above average for May. The nationally averaged overnight low temperatures during May were 52.5°F, or 5.1°F above average. That is 2.0°F warmer than the previous record set in 1987.  Daytime highs set records. It was 100°F on May 28 in Minneapolis, Minnesota. That was the earliest 100˚F on record.

May brought record and near-record precipitation to the southeast and mid-atlantic states in connection with the early storm Alberto. Drought conditions persisted along the West Coast, Southwest, Southern Plains, the Northeast and parts of the Midwest. Warm temperatures caused flooding by melting the high snowpack in parts of Idaho, Montana, Washington and Wyoming.

Future Prognosis

What will the summer months bring? That is not easy to predict. The NOAA Climate Prediction Center is charged with that responsibility. They issue a set of maps for the coming months based on input from a number of climate models. The predictions for June 2018 temperature and precipitation indicate much of the country will likely face above normal temperature. The contour line marked 70 around the A means there is a 70% probability that region will be above normal in temperature for June.

Precipitation expected in June varies around the country. The middle Atlantic and southeast have a 40% probability of above average precipitation. It is likely to be drier than normal in the areas marked B.

14 thoughts on “U.S. Climate | April and May 2018

  1. Interesting Jim – Illinois has been incredibly warm for this early in the season. We’ve had good rainfall to keep things green but we’ll see. Thanks for the info

  2. It has been crazy weather nationwide. I’ve finally thawed out after this extra-long winter, and we weren’t as cold as you were. Climate change means instability and that is what I figure I need to get used to.

  3. Very interesting post Jim. It is hard to know what to expect. I am hoping we don’t have a fire season like last year. Thanks for posting the weather charts. Take care.

    • Thank you. We’ve received some much needed rain the past couple of days. More on the way.

      I hope you don’t have a fire season like that, too. We smelled it all the way down here. It must have been powerful up there.

      • It was very bad. Lisa, like many other people, ended up in the hospital with breathing problems. The skies were smokey the better part of three months.

  4. These data only reinforce the impression I’ve had for some years now, Jim, that the Southwest has become a dangerous place to live. The power grid is creaky and vulnerable, even without mention of terrorism. Am I overreacting?

    • I don’t think you are overreacting. I think that is a realistic appraisal. For too many years we have neglected the maintenance and improvement of infrastructure. It is like taking care of your car or house or body. Don’t take care of the day to day, some day it will force you to pay a high price.

  5. I was cheered to see a neighbor having solar panels installed on his roof, and many in my neighborhood are using native plants with their extensive root systems and no need for fertilizer or water. Now if we could convince people they don’t need to drive their kid to school in a Hummer….

  6. It really isn’t realistic for so many people to continue to live in arid areas. This means those of us who live where there is abundant water probably need to get ready for an influx of people.. Worldwide populations will have to shift and if this is planned for, it can be accomplished peacefully. Or we could just let things play out, and end up with famines and refugees and war.

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