National Weather Service forecasters say the latest the mercury ever reached 100 in Sacramento was on this date 21 years ago - Oct. 10, 1991.

Today's daytime maximum is expected to fall far short of the 100-degree mark. A high of only 77 degrees is forecast for Sacramento.

A Bee count of the number of 100-degree days indicates that downtown Sacramento has experienced 19 days of century mark readings this year. The average number of Sacramento days with 100-degree readings or higher in a year is 22, according to the NWS.

Here's 100-degree weather breakdown for 2012:

n May: 0

n June: 3

n July: 5

n August: 9

n September: 0

n October: 2

The detailed, 7-day forecast from the NWS:

Today: Mostly sunny, with a high near 77. Southwest wind 5 to 8 mph.

Tonight: Partly cloudy, with a low around 54. South wind 8 to 11 mph.

Thursday: Mostly sunny, with a high near 72. South southwest wind around 8 mph.

Thursday night: Mostly cloudy, with a low around 55. South wind around 11 mph.

Friday: Mostly sunny, with a high near 74. South wind 3 to 7 mph.

Friday night: Partly cloudy, with a low around 54.

Saturday: Mostly sunny, with a high near 78.

Saturday night: Partly cloudy, with a low around 53.

Sunday: Mostly sunny, with a high near 81.

Sunday night: Partly cloudy, with a low around 56.

Monday: Mostly sunny, with a high near 83.

Monday night: Mostly cloudy, with a low around 56.

Tuesday: Mostly sunny, with a high near 83.