Question
I live in MA and it's about 80s now in summer. I read that it's not a good idea to grow new grass during this time of year. Is this correct? I have several thin areas I would like to see fuller grass. I've applied seed back in spring but I missed a few spots that I would like to fix. Do I have to wait until fall?

Answer
Good afternoon Hank:
I live in central Illinois. We could really use some of your 80 degree temperature. It has been in the mid 90's here for the last eleven days.
Timing is critical to assure success when seeding lawns.
Cool Season Grasses, as you have in Maine, should be planted In the fall between late August and early September. The next best time is in the spring for the entire month of  March through mid April. Seeding in late spring through mid-summer often leads to stress problems.
Cool season grasses struggle during the summer. They may or may not go dormant during the winter cold.  In general the best time is when temperatures are in the optimum range for rapid germination and for rapid development after germination. In the northern part of the USA grass seed germination is optimum when temperatures are in the range of 60 to 85 F.
For successful overseeding, it is critical that seeds be placed into contact with the soil, whether seeding into live or dead turf. Seeds scattered on top of live or dead turf rarely produce a decent stand of turf.
To renovate successfully, adequate water must be available from seeding through germination. Try not to allow newly overseeded areas to dry once watering has commenced. Maintain a constantly moist seedbed with frequent watering of short duration. As newly germinated seedlings begin growth, decrease watering frequency and increase the duration to encourage rooting.

Have a good lawn!
Floyd McMahon