Another day into an excessive heat advisory. That is for parts in San Diego. This is KPBS Midday Edition . I am Maureen Cavanaugh. The top story , as the nation watches Texas and Louisiana cope with the record-setting amounts of rainfall and letting, San Diego as experienced record-setting record of its own, the high pressure system over Nevada has set up conditions for an excessive heat warning for the County inland valleys and foothills and deserts through Friday. Joining me is Alex Tardy with the national weather service. Welcome. Thank you for having me on. August and September is the hottest month. Is a heatwave like this to be expected ? We are getting heat waves like this. Every year, -- this has set the stage where it is very unusual. September and October, we are use to that here. The heat is on because that is what we call the wind season and that brings the hot temperatures to the coast. What makes this system or high pressure system that you refer to unusual is the large coverage of the warm air and the duration. We are going to talk about the same high pressure system all the way through September 10. That is a long time. Yes. What we notice is that it is humid and foggy along the coast but searing hot temperatures and dry conditions are inland. How do we get those in the same general area? That is a good observation. We call them microclimates and we see those. Out in the deserts, for the past four days has been 115 degrees. Humidity has been unusually low considering that is the monsoon thunderstorm season. Go into the inland valleys, the Valley Center, for example, Ramona, 108 degrees. The humidity is relatively low. There has been a fire concern in those areas. Go close to the coast, west of the 15. A lot of people live there and it has been muggy. The mightiness comes from the marine layer. That is really shallow right now. It is a small area of high humidity combined with the temperatures which gives us a heat index. Yesterday, the heat index was 106 degrees. Even though the air temperature was 99 or 100, when you add the humidity to it, the different microclimates -- here is a good one. Catalina Island, it was in the 80s which is warm. Where the airport is, it was 100 yesterday. Above the fog and marine layer, it is burning off on the coast and even the beaches and it allows the cloak -- the beach to get 80. How high is San Diego's fire risk ? It is elevated. For a couple of reasons. The prolonged duration of the heat has an accumulative impact. It's not just animals but also the fire weather danger because it is day after day after day of hot temperatures. When you do not have a lot of moisture, fires like to burn when the humidity is low. When we have these extreme temperatures over 100, it's set that up. The wind is light. The seabreeze is light. There is not much Santa Ana wind. The good news is the wind is light. If we do get a fire, they should be able to jump on it quickly. You just mentioned Cowling -- Catalina, how much of California is getting the same heatwave? It is all of California from Northern California all the way up to us. And just to add insult to injury, the same high pressure system rebuilt Labor Day weekend over Northern California comes down to Southern California Monday and Tuesday and then rebuilt again. We will talk about this for the next two weeks. Two weeks of hot weather like this ? Very close to this. We have some relief Thursday and Friday and temperatures may lower a few degrees on the coast and come back on Saturday and maybe more relief but when we get the relief, it will be more humidity at the same time. It is a double-edged sword. You know, we should not feel that badly about this. There are parts of the nation right now that are really suffering with the weather. I mentioned the Gulf Coast. I want to ask you a question about Harvey. We know the storm has moved fairly slowly and picked up huge amounts of moisture from the warm water in the Gulf of Mexico. Is they -- there a particular weather pattern that is sustaining the storm ? Ironically, the weather pattern is the roadblock. They call it the dog days of August. The same high pressure system that is covering the West Coast in California and Utah and Mexico, that high pressure system literally blocked Harvey from going anywhere inland and North. Actually, it turned around. The high pressure system is effectively blocking the weather pattern from the gulf. It is bad enough that you know, the typically, you do not see hurricanes move quickly but when you have that massive of a high pressure system, if locks it and has allowed it to stall for several days now. We have seen record-breaking rainfall, 51 inches of rain breaks the record for any tropical cyclone in the United States. Just last night, the Beaumont area salt 22 inches of rain in less than 24 hours. We see a remarkable rainfall, not just hourly but daily and storm totals. A lot of it is attributed to the warm gulf, but the system was blocked by our same high pressure system. I want to thank you. I have been speaking with Alex Tardy with the National Weather Service. Thank you so much. Thank you for having me on.
Temperatures across San Diego County will drop a degree or two Wednesday following a second straight day of record-breaking heat. But with the mercury still hitting triple digits, the slightly cooler weather "won't be very noticeable," the National Weather Service said.
An excessive heat warning for most of the county is still in effect through Friday night, while the mountains and beaches are under a less-serious heat advisory during that same period.
"Expect another hot one today," the NWS said, adding the weather could cool off even more Thursday — but still remain very hot — before getting hotter again Friday and through the weekend.
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On Tuesday, Ramona hit 108 degrees, setting a new Aug. 29 heat record that was previously 105. The all-time record there is 111 degrees.
Other high temperatures included 117 in Ocotillo Wells, 114 in Borrego Springs, 108 in Valley Center, 106 in Alpine, 105 in Campo, 103 in Poway, 102 in El Cajon and Santee, 101 in Escondido and 100 in Fallbrook. Mt. Soledad, poking over the marine layer, hit 87 degrees, though the coastal communities under the marine layer stayed much cooler.
Meteorologists attribute the recent run of hot weather that began over the weekend to a "goliath" high-pressure system that moved south from northern Nevada, pushing heat toward the coast and squashing the marine layer. That system is "nearly stationary" now, bringing stifling hot weather to the entire Southwest.
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High temperatures Wednesday will be 77 to 82 degrees at the beaches, 89 to 94 inland, 94 to 99 in the western valleys, 100 to 105 near the foothills, 96 to 102 in the mountains and 111 to 116 in the deserts.
The NWS reminded residents that during an excessive heat warning "persons working outdoors or those without access to adequate air conditioning will be more likely to experience heat-related illness, such as heat exhaustion. Some heat-related illnesses are serious enough to require hospitalization and could become fatal if left untreated."
The weather service reminded residents to never leave kids or pets unattended in cars; drink more water than usual and avoid alcohol, sugar and caffeine; wear light-colored clothing and a wide-brimmed hat outdoors to keep cooler; and take frequent rest breaks in shaded or air conditioned environments.
