I would not apply glyphosate on a day it is supposed to rain. On most foliar herbicides, I've found that the percentage kill will decrease, even after the allotted time has passed. If I cannot get at least 8 hours without precip, I hold off. I strongly prefer at least 24 hours after application. The only exception to this is when I am applying picloram. Then, I prefer to have at least some form of precipitation within the week, within a day or two if possible.

Applying a granular fertilizer right before or after applying herbicide won't hurt anything. If that is when you can get it done, do it, although it is better to fertilize right before, during, or after planting.