Why are my windows yellow in spring?

UF/IFAS Extension in Pinellas County names the yellow on a car plainly: very likely pollen from a pine or oak tree. Outdoor glass sits in the same air, so that is the likeliest answer for a window too, though no UF/IFAS page read for this answer speaks about glass.

The months fit too. UF/IFAS says Florida's pollen season peaks from January to June, starting in North Florida and creeping south, and peaks in South Florida from February to May. A yellow film that appears during those months fits that calendar.

The yellow on one house and the next can differ, and UF/IFAS gives the reasons.

The species behind it shed on a large scale. FR268 says pines and oaks produce huge volumes of wind-dispersed pollen, light enough to cover several miles on the wind, so the tree behind a yellow pane need not stand in the same yard. UF/IFAS's news post says density varies by location, due to tree species, local climate and elevation, and FR268 adds that quantities vary from tree to tree and from one season to the next, and that a mild winter may cause trees to pollinate earlier. Whether that same dry powder clings once it lands, and what rain and wind do to it, is answered on does pollen stick to windows.

A number worth reading carefully belongs to a specific place.

A UF/IFAS Extension agent in Hillsborough County, quoted in the same news post, puts the height of pollen season at March and April, and says it tapers off in the summer and ramps back up with grasses in the summer. The post gives that line to the agent, and it is printed here as the agent's statement, not as the peak for Naples or for South Florida, where the post's own sentence is February to May. The agent puts no dates on the summer grasses and does not mention the rainy season.

Naming pine or oak pollen as the likely cause is not the same as diagnosing a particular house.

Pollen is a dry deposit, and this page cannot tell from a description whether a given yellow haze is pollen or something else. A dull film that is not pollen has its own answer at what is the film on my windows, and why glass can look different when the sun is low is taken up at why windows look dirty when the sun is low. NOAA's Naples rain and temperature normals sit on the site's month-by-month calendar.