A Few More Words About Rainfall

Thirty years ago I had a neighbor who long before had been a writer for The Miami News. In 1926, her boss gave her a plum assignment – the lead story in the women’s section of the issue for Sunday, September 19. The young reporter chose to write a piece about home remodeling, ordinarily an upbeat topic. But on the day before her story ran, Miami was hit by the unforgettable hurricane whose eye passed directly over the city. My neighbor was embarrassed by the fact that her advice on remodeling might seem to be trivializing the plight of storm victims, many of whom now lived in buildings left looking like dollhouses, sides ripped off for all to peek into.

This was clearly an instance of inadvertent bad timing, and last weekend there was a little bit of that on this website. While we were preparing an article with advice on how to deal with the drought, the skies opened up, and at Richard Lyons’ Nursery it rained hard two more times that day. And rain fell again the next several days! It appeared that our drought might be ending, but dry conditions have returned. This might be a good time, then, to take a little closer look at rainfall patterns in southern Florida, so that you might be better apprised of those times of year when you need to pay special attention to irrigation.

As mentioned last week, the rainy season in southern Florida comprises parts or all of six months. Rainfall patterns here are like those found in much of the Caribbean Basin, where traditionally dual peaks occur during the rainy season. In our region, for many years those peaks have been May-June and September-October. But something has changed over the past 35 years or so. Now the peaks are more closely spaced. The rainfall totals for June-July (16.17 in Miami, 16.14 in Ft. Lauderdale) and August-September (18.74 in Miami, 16.03 in Ft. Lauderdale) now exceed those of May-June and September-October.

But one thing has remained relatively constant: July is the driest of the months entirely within the rainy season, and that leads to a very stressful time for plants. According to the National Weather Service, normal rainfall this month is 6.50 in. in Miami and 5.98 in. in Ft. Lauderdale. That would be nearly record-breaking in a place like El Paso, Texas, but it is fairly light in a region where so many tropical ornamental plants are grown. The risk is that, even in a typical July, we often experi-ence a stretch of five days or so in which no rainfall occurs, and that can devastate containerized material. So homeowners must keep an eye peeled toward signs of drying in their special plants.

It is also important to know the rainfall patterns for the rest of the year, because the low rainfall and breezy conditions of the dry season also impose the need to monitor plants, whether inground or containerized, for moisture loss. Following is the complete list of National Weather Service monthly rainfall averages for Miami and Ft. Lauderdale, respectively, covering the period 1980-2010. Even though annual rainfall during that time actually increased over historical norms, to 61.15 in Miami and 62.18 in. in Ft. Lauderdale, the continued low levels of dry-season precipitation underscore the necessity for diligence in watering practices.

January                   1.62                  3.63

February                 2.25                   2.96

March                     2.25                   3.36

April                       3.14                   2.89

May                        5.34                   4.65

June                       9.67                  10.16

July                        6.50                    5.98

August                    8.88                    7.44

September              9.86                    8.59

October                  6.33                    6.82

November               3.27                    3.24

December               2.04                    2.46