There are many factors that can add rust or iron to drinking water. Any rust addition happens in the distribution pipes after it has left the treatment plat. There may be a water main break in your area, there could be construction that is affecting water lines, or it may be caused by mandatory hydrant flushing conducted in the Spring and Fall annually.
If you experience rust in your water contact the Water Distribution Department. After contacting the department run your cold water for ten (10) minutes. If it clears up, great! If the problem persists the City will need to flush a hydrant near your location to get rid of the rust.
NEVER use your hot water when your are experiencing rust in the water. Doing so will draw the rust into your water heater tank and potentially cause problems.