|When is the first frost in my area?|
|You can check this, as well as the typical last spring frost date, using the maps at the following official weather data web site. You may need to cut and paste the complete url into your browser to make it work correctly.
I would say somewhere in the first half of October. Keep in mind this is not going ot be completely accurate every year as it depends on the overall weather but also on the microclimate where your garden is sited.