SYRACUSE, NY (WSYR-TV) — On this first day of Fall, there are Frost Advisories up for parts of Central New York Friday night.

So far, Lewis, Northern Oneida and Otsego Counties are under advisories. Temperatures are expected to drop into the low to mid-30s with frost possible

While temperatures in the Advisory areas may only drop into the mid-30s overnight Friday, how can frost happen?

There are two important things to keep in mind.  First, on cold nights like Friday night, the coldest air in the lower atmosphere will sink close to the ground because it is denser or heavier. 

Secondly, most outdoor thermometers are mounted several feet above where this coldest air settles.

Some of our computer model data is hinting that the mid-30s may show up in other parts of Central New York so additional counties like Tompkins, Cortland, and Chenango, may be added to the advisory list later today.

In Syracuse, temperatures end up in the low to mid-40s by Saturday morning so no frost is expected.

The average first date that Syracuse can expect to see temperatures drop to at least 35 degrees is October 7 with the first 32-degree day coming ten days later.