Climate signals #1 and #2: Atmospheric moisture increase and extreme precipitation Increase

As temperatures have climbed, so has the amount of moisture the air can hold. The northern hemisphere has had increasingly warmer and more humid summers, and the global area covered by extreme water vapor is increasing significantly.[12] Unusually humid air also increases the risk of heavy rainfall because storms have more moisture to work with. Rainfall rates from such storms can be high, which increases the risk of flash flooding.

Observations consistent with climate signals #1 and #2

• Heavy rain late on June 16 to early June 17—of 4 to 8 inches and some reports to around 11 inches—in northeastern Minnesota and northwestern Wisconsin led to flash flooding that washed out highways.[19][20]
• The Nemadji River crested at its highest point on record in Superior, Wisconsin, topping more than 31 feet. The previous record, set in 2011 and again in 2012, was 27.37 feet.[21]
• Isolated regions near Solon Springs, Wisconsin, saw rainfall totals up to 12 inches on Sunday, June 17. Rainfall totals between 6 and 12 inches in just a few hours in this region are so rare you would expect totals this high only once every 100 to 1000 years, according to station records spanning 1948-2005 in Drummond, Wisconsin.[22]
• Houghton, Michigan, received 4 to 7 inches of rain in seven hours.[21] Based on past observational data, you would only expect rainfall rates this high once every 200 to 1,000 years.[23]