When to Plant – If you want a green lawn by summer, you can plant grass seed in New York between early April and mid-May. As the grass begins to establish itself, even a light frost will not harm it. Early fall is the optimal time to plant grass seed in New York (mid-August to mid-September).
Warmer soil temperatures (between 60 and 70 degrees Fahrenheit) and consistent precipitation at this time of year promote faster germination and deeper roots. This will aid the grass plants in establishing themselves before winter arrives. You will also have less competition from crabgrass and other summer weeds.
When the soil warms up in mid- to late-spring, grass plants will develop deeper roots, grow thicker, and build up food reserves to prepare them for summer stress. 
What temperature is required for grass seed to germinate?
The ideal soil temperature for seed germination is between 50 and 65 degrees Fahrenheit, which corresponds to daytime temperatures between 60 and 75 degrees Fahrenheit. However, if the soil temperature is significantly below 50 degrees, the seeds will remain dormant and not germinate.
