Last week I wrote about some calculations to find the inflection point when the temperatures change from being better for warm-season grass (like bermudagrass, seashore paspalum, or zoysia) to being better for cool-season grasses (like perennial ryegrass, creeping bentgrass, or kentucky bluegrass). This inflection point can be represented on a chart as the minimum value for the cumulative sum of the warm-season growth potential (C4GP) subtracted from the cool-season growth potential (C3GP). Over a long time series, the median date for this inflection point in Palm Springs, California, is October 13.
At the time I made the calculations in late October, Palm Springs hadn’t reached the inflection point yet. I was curious when it happened, so I downloaded the most recent data today. It seems the inflection point this year, using data from the airport, happened on October 29.