The immediate cause of your inability to see stars is poor transparency, likely exacerbated by light pollution. It is certainly possible for transparency to get so bad that it blots out anything fainter than Saturn even at a dark site, but light pollution makes that much more likely. At a light-polluted site poor transparency gets you both coming and going -- not only does it dim the stars, but it also brightens the sky.
It's easy to recognize poor transparency during daylight hours. When the transparency is good, the sky is deep blue. Bad transparency makes the daytime sky either white or gray.
Poor transparency can have a multitude of causes. Natural sources include dust storms in the desert, smoke from forest fires, and volcanoes. All of those can easily loft into the stratosphere, where they can (literally) travel all the way around our planet. Dust storms in the Gobi are a common cause of poor transparency in California, just as dust storms in the Sahara often cause poor transparency in the Caribbean.
Humidity per se doesn't necessarily cause poor transparency, but the combination of high humidity and artificial air pollution is particularly bad. If you have had abnormally high humidity recently, there's a very high likelihood that it's related to your poor transparency.