Today will be the least hot day of the week, with a high of 89. We’ll have a 20 percent chance of a shower or thunderstorm this afternoon, with mostly sunny skies.

Expect fog after 1 a.m., and a low of 70.

Then the heat begins to build. Along with the heat, we’re going to have poor air quality, too. We’ve had a number of code yellow days, meaning the air is moderate. Friday and Saturday will be code orange days, meaning the air quality is unhealthy for sensitive groups. Those groups include children, active adults and those with heart or respiratory disease, including asthma.

The main problem will be ozone, but particle pollution will also be in the moderate range.

Friday will be sunny and hot, with a high of 92 and southwest wind at 3-6 mph. Friday night will be partly cloudy and 72, with more wind from the southwest.

Saturday will be mostly sunny and 95, with west wind at 3-5 mph. There will be a 20 percent chance of showers and storms after 10 a.m. The heat index will make it feel like 100-105 degrees.

Saturday night also has a 20 percent chance of showers and storms, before 11 p.m. The low will be 74.

Sunday will be mostly sunny and even hotter, with a high of 97. The heat index could go as high as 108 degrees. The low will be 74 again.

In the high heat, drink plenty of water, avoid prolonged outdoor activity, check on family and neighbors to make sure they have a a way to manage the heat and don’t leave pets in the sun.

Monday will be 97 again, with a mostly sunny sky. A 30 percent chance of showers and thunderstorms is possible after 4 p.m. The same chance of rain continues Monday night, with a low of 74.

Tuesday’s high will be 93, with mostly sunny skies and another 30 percent chance of showers and thunderstorms. The chance of rain lingers through Tuesday night, when the low will be 73.

Wednesday, the high will be 92, with the usual 30 percent chance of showers and storms and mostly sunny skies.