Hi,
I was going to install hardwood ~7 months ago, but for certain reasons it was postponed, so now it has been acclimatizing for almost a year in a normal house with heat/air-conditioner. I bought a moisture meter from general. I made many tests on various wood and in various areas, I think it responds adequately. More or less accurate to get an average picture about condition of wood.

1st floor
I already have some hardwood on 1st floor from previous owner. Btw the basement below is unfinished (everything in basement is higher in moisture ~9-11%). Sub-floor for 1st floor is about 10% and the hardwood is 9%.

2nd floor
I'm installing new oak 3/4 (3 1/4" width) for second floor. The reading from the meter says OSB sub-floor (3/4) is ~5.7-6% and the acclimatized wood is 5.4-6.7%.
I heard the moisture for oak floor preferably should be ~8%.

It is strange because it is summer here in Ontario, Canada and the humidity is kind of low... There wasn't much rain. Do I expect that the humidity will be much lower in the winter?? Or the humidity will be higher next summer so the boards will cup??

Is it safe to install such floor with current conditions??? Should I make some rows with spacers? Or with such MC it's ok even if the MC will go up to 8%??? Will the cup severely from 2% increase?

Thank you!

The floor is safe to install.