I think it has quite an effect in the summer because the city is cooled by being near the ocean but the western suburbs get super hot, so a 10 degree difference might not be unusual at times, for two places about 30km away.
London is regularly 3-4° warmer than the towns and village that border the M25 ring road. You can genuinely feel the difference when you take a train into the city and vice versa.
Not terribly relevant to your point, but: Noon is actually a time in the day where it is still getting warmer. Temperature usually peaks around 16:00 or 17:00 in the summer.
From the article: 'If the urban heat island theory is correct then instruments should have recorded a bigger temperature rise for calm nights than for windy ones, because wind blows excess heat away from cities and away from the measuring instruments. There was no difference between the calm and windy nights, and one study said that "we show that, globally, temperatures over land have risen as much on windy nights as on calm nights, indicating that the observed overall warming is not a consequence of urban development."'
This is really surprising to me. Not least because, on a sunny day, SF can go from pleasant to brutal as soon as a breeze kicks up.
> Research has been done in a few areas suggesting that metropolitan areas are less susceptible to weak tornadoes due to the turbulent mixing caused by the warmth of the urban heat island.
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[ 2.8 ms ] story [ 44.4 ms ] threadExample: http://wetterstationen.meteomedia.de/?station=104870&wahl=vo... (the forecast diagram for my local weather station)
This is really surprising to me. Not least because, on a sunny day, SF can go from pleasant to brutal as soon as a breeze kicks up.
> Research has been done in a few areas suggesting that metropolitan areas are less susceptible to weak tornadoes due to the turbulent mixing caused by the warmth of the urban heat island.