The fall is a beautiful time of year (football season doesn't hurt either), but it does have some interesting effects of turfgrass. Cooler temperatures at night can cause warm-season grass growth to slow, while conditions optimize for cool-season species. Along with temperature, day length also begins to shorten. This means that less light is available for plant use, which can be reduced even further by extra shade cast by buildings (north side) and other plants.
What can happen during these conditions? Moisture from dew or irrigation may take longer to evaporate from leaf surfaces, creating an ideal environment for disease outbreaks (which can vary depending on the grass species). Low light can also trigger changes in the turf itself, leading to elongated leaf blades (which are also thinner). This growth can lead to scalping, which can affect turf health and aesthetic. If identified early, many of these issues can be preventatively treated. Fungicides and plant growth regulators can be used to target problematic areas. Cultural practices should also be adjusted, including raising the height on mower decks. Depending on the local climate, these factors should continue to be monitored until dormancy (warm-season) or changes in growth rate (cool-season).