Is it too late now to overseeding the lawn?
Hello and thank you for contacting the Toronto Master Gardeners with your question.
Yes you still have time to do overseeding of your lawn, but it would be recommended to try and get it done by this weekend. We are still in a nice mild pattern through the end of the month which should allow for a robust germination going into November with the right amount of watering.
I have added a reference link below from The Professional Lawn Care Association of Ontario, which provides you with tips on overseeding and many other aspects of growing a healthy lawn.
Best of luck with your lawn.