Cabo San Lucas weather, as is true of Baja California weather in general, can have an element of unpredictability to it. It might be dry and humid at one moment, and then change to cool and windy in short order. Generally speaking, however, this is mostly a warm weather destination, and it can get quite hot during the summer season. As for rainfall, that is pretty minimal year round. In fact, most months usually fail to register much of anything in the way of precipitation.
Summer: Summer isn’t exactly the peak tourism season in Cabo San Lucas. This is partly due to the fact that it is the start of hurricane season. It also has something to do with the fact that it gets pretty hot in Cabo during the summer. Average highs in the mid-90's are what June, July, and August are all about.
Fall: Autumn is another season that travelers tend to ignore when planning Cabo San Lucas vacations. After all, this is also hurricane season, and during the first half of fall in particular, it can get rather hot. Average highs in September are around 95 degrees, for example, and October sees average highs of around 90 degrees. It should be said that there arguably isn’t a bad time to visit Cabo when it comes down to it, so fall or summer shouldn’t necessarily be neglected.
Winter: While it can get cold and windy in Cabo San Lucas during the winter season, this is when the peak tourism season begins. The end of December is more specifically when tourists begin pouring in. On most winter days, it is actually warm, with temperatures usually settling somewhere in the 70's. Many consider this to be the ideal time for such things as scuba diving excursions, visits to area missions, and trips into the mountains.
Spring: Spring is also a popular time to take Cabo San Lucas vacations. Early spring and the Spring Break period are especially busy times. Things start to calm down after Easter as the low season starts to take over. As is true in winter, the promise of warm, but not terribly hot days is what you can generally expect in Cabo during the early spring. The average high in March is around 77 degrees as opposed to 86 degrees in May and 89 degrees in June. Spring, it should be noted, is the driest season on average. Most months get hardly any rainfall.