We'll have a couple more days in the mid-80s this week. But by Thursday, after a frontal passage Wednesday evening into Thursday that could trigger some showers and storms, the season's first chilly Canadian cold front will bring Central Maryland a taste of autumn. High temperatures from Thursday right through the weekend will struggle to reach 70 degrees.

Air conditioners, at least, will be silenced. But a few of us may be tempted to awaken the heaters as overnight lows drop to the low 50s, and even into the 40s to the north and west of I-95. I see we already picked up the season's first two degree-days last Tuesday. The high that rainy day was 64; the low was 62, for an average of 63 degrees. That was 8 degrees below the norm. 

We'll have a bunch more before the week is out. Some parts of the country may see their first frost this week. But not us.

The average highs for Baltimore at this time of year have slipped into the upper 70s. The average lows are now in the 50s. So it really is time for us to have some days like those we'll see by week's end. At the same time, it's still possible for highs to reach the 90s.

Every date in September has a record high of 91 degrees or more. The record for the month is 101 degrees, reached on Sept. 7, 1881. 

Finally, I need to acknowledge the beautiful Harvest Moon that rose over Baltimore last evening. Busy as we've been with earthquake, hurricane, Grand Prix and flooding, this one got past me.

The Harvest Moon is defined as the full moon closest to the autumnal equinox. The equinox this year occurs at 5:06 a.m. on Sept. 23. That's 11 days after the September full moon. The next full moon occurs on Oct. 11. That's 18 days after the equinox, so that one's the Hunter's Moon.