It is time to increase your sugar water mixture
3 parts water to 1 part sugar. This will provide additional calories for the hummers during their long migration flights. Most ruby-throated hummers make the 500 mile flight across the Gulf of Mexico to winter in Central America. But, some choose to take a different route. Many come down from Canada on a western route through Texas and cross into Mexico directly. Others reach the coast and turn west traveling around the Gulf so they do not have to make the water crossing. Still others circle east and hop through the Caribbean Islands into Cuba so their journey across the ocean is not so long.
Do not take your feeders down until Fall migration is complete. Leave your feeders out until you go for 2 weeks without seeing any hummers.
I usually leave my feeders out until the end of October. You will not delay their migration by leaving the feeders up. Hummingbirds know when to return to their winter homes. The weather turning colder is not a factor in causing the hummers to migrate. It is thought that changes in daylight hours drive the urge for the hummers to start their migration. The changes in daylight trigger an increase in the hummers appetite which helps them pack on fat reserves for the long flight ahead.