May 2006 - A month of extremes

May 2006 - Winter’s Last Hurrah or Summer’s Early Arrival?

May 2006 was a month that will stick out in the minds of Central Indiana residents for some time. The month saw extremes ranging from searing heat and sweltering humidity to bone-chilling damp cold, with just a few days in between! While Spring will typically bring highly changeable weather to the Midwest, seldom does it bring weather this volatile.

The overall totals for the month do not do the variability of May 2006 any justice. As it goes down in the record books, May ended up slightly cooler than normal and very close to normal for rainfall.


May 2006 saw an average temperature of 61.3 degrees, which was below normal by 1.3 degrees. 4 of the past 5 Mays have brought below normal temperatures to Indianapolis. While this year’s monthly average was only slightly below average, there were periods of the month that saw temperatures that were much colder than normal.

Temperatures were below normal every single day from May 11th through May 24th, sometimes as much as 15 degrees below normal. This cool spell peaked between the 12th and the 14th, when high temperatures failed to reach 50 degrees on the 12th. These temperatures would be normal for late March. The culprit was an unseasonably strong area of upper low pressure that refused to budge for days on end.

Just when it seemed this cloudy, dreary, and cool period would never end, it did, and quickly. A strong area of summer-like high pressure had built up over the Plains states, and finally became strong enough to shove this upper low out of the area. And when it did, the temperatures did a complete shift in the opposite direction. From the 25th on through the end of the month, every day was above normal, and sometimes as much as 12 degrees above normal. This made for an extremely warm and humid Memorial Day weekend, as highs peaked just shy of 90 degrees for four days straight.

Two temperature records were broken this month. Both were for Record Coolest High Temperatures, on May 12th and 13th. The highs on these days were 49 and 50 degrees, respectively. A high temperature that fails to reach 50 degrees during the month of May is a fairly rare occurrence, the last time it has happened was 15 years ago in May 1991.


Monthly rainfall in Indianapolis ended up at 4.34 inches, which was below normal by 0.02 inches. The period of May 9th through 19th saw an amazing 11 consecutive days that saw rainfall. This is the third longest streak of consecutive days with rainfall during the month of May.


After the severe weather season rocketed out to a ferocious start in April, things settled down a bit in May. There were still 8 days on which thunder was heard in Indianapolis. May 25 and 26th both had numerous severe weather reports ranging from hail the size of golfballs to thunderstorm wind gusts of over 60 mph to sightings of funnel clouds.

This was a welcome break for residents of Indianapolis who suffered through several large hail storms during the month of April.

What’s Next?

The official summer outlook from the Climate Prediction Center has shown a forecast of "Equal Chances" for the Midwest, including all of Indiana. This means that for both temperatures and precipitiation amounts, the chances of values being above, below, or near normal are equal. As the La Nina weakens and ends, the signals for a summer forecast are weak. And so there is no enhanced likelihood towards a specific forecast of warmer or cooler, wetter or drier.

It is important to remember that summer in Central Indiana always brings temperatures well into the 90s and frequent bouts with high humidity. In addition, this summer Atlantic Hurricane forecast is for an active year, and individual tropical remnants can some times track into the Midwest and bring copious rainfall amounts. One thing for this summer is certain - expect a little bit of everything, in true Central Indiana fashion!


Prepared by Climate Services Focal Point, Logan Johnson

With data and input  from HMT Staff and Service Hydrologist

Temperature and precipitation records at Indianapolis cover period 1871-2006

Normal refers to the 1971-2000 30 year average

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