Daylilies are classified as "wet" stigma species. That means that for daylily pollen to work the stigma needs to be moist from the stigmatic fluid. There is scientific information about some of the temperatures at which pollen works and therefore stigmatic fluid is present. To work, daylily pollen needs that stigmatic fluid. Some of the daylily species flower in the early spring when temperatures are lower than 80F so the stigmatic fluid will be present at temperatures that are lower than 80F. Daylilies have been pollinated at room temperature (72F) and the pollen tubes have grown successfully. Stout pollinated some daylilies at 6 am in New York city in early June when temperatures will have been in the 60s and pollen tubes grew without delay. Arisumi grew daylilies at 75F and pollinations were successful. Some daylilies first open their flowers at night and are naturally pollinated by night flying insects such as moths. The temperatures at night are likely to be much cooler than 80F. Stigmatic fluid will be present at temperatures substantially lower than 80F. I know of no objective evidence that the fluid can dry and block the passageway. Stout successfully pollinated some daylilies at 9 pm on days when the afternoon high temperatures will have been 86F to 90F or a couple of degrees above 90F.