The mild summer of 2010 is becoming a distance memory now that the fall season has arrived.
The heat is enough for the National Weather Service to issue an excessive heat watch in the Bay Area through Wednesday night.
The cities under the advisory are in the inner Bay. Think San Mateo, Richmond, Oakland, Hayward, Fremont, Mountain View and Palo Alto. Daytime temperatures are expected to reach 90 degrees there and yes the calendar says October.
Fire danger is also high in the North and East Bay hills. Red flag warnings were lifted Wednesday morning, but the danger remains due to hot and dry conditions. The warnings decreased when the wind died down.
You can blame a ridge of high pressure combined with an offshore flow for the exceptionally high temperatures.
NBC Bay Area's Rob Mayeda says look for the sea breeze to turn on by this evening, leading to noticeable cooling around the inner bay for Thursday. All areas will cool down significantly approaching the weekend as high pressure gives way to an approaching trough of low pressure. Not only will we see much cooler weather, but may even manage a few showers across the North Bay heading into Monday.
The weather also caused the Bay Area Air Quality Management District to issue a Spare the Air alert for Wednesday. It's the 10th smog alert this year.