According to multiple sources, the following fruits are in season in September:

• Apples
• Blackberries
• Blueberries
• Cantaloupe
• Figs
• Grapes
• Mangoes
• Nectarines
• Peaches
• Pears
• Plums
• Raspberries
• Red currants

Its worth noting that September is a transition month between summer and fall, so some summer fruits like strawberries and peaches may still be available, but not for long as the season turns to fall. Additionally, some sources mention that avocados and bananas are available year-round, while others mention them as being in season in September. Overall, its best to check with your local farmers market or grocery store to see what fruits are in season in your area.