Sunday, October 1, 2017

Grand Rapids, Michigan, climate update for September 2017

Max Temp: Actual 96, Mean 89
Min Temp: Actual 41, Mean 37
Av Temp:   Actual 66.5, Mean 62.7, YTD Actual 53.9, YTD Mean 51.1
Precip:       Actual 0.66, Mean 3.55, YTD Actual 24.98, YTD Mean 26.28
CDD:         Actual 136, Mean 75, YTD Actual 708, YTD Mean 685

In short year to date we are slightly warmer and dryer than the mean.

Average temperature is running 5.5% ahead of mean and cooling degree days about 3.4% ahead of mean. The rain deficit is running about 4.9% behind the mean. For average temperature year to date, compare some of the hotter years 2012 at 56.4, 1931 at 54.2 and 1921 also at 56.4, the average of which is 55.7. We are still 3.2% cooler than that in 2017.

Last season's average ONI value was -0.266, the lingering effects of the five month long Weak La Nina, indicating a very slightly cool ocean in the tropical Pacific over the last year. The preliminary read of the first value in the new season is -0.1.

Despite the heat wave we experienced in September, I still used 8% fewer kWh this September than last and stayed comfortably cool.