The heat-island of smaller towns such as Reading will be removed by lower wind speeds. If there is a light breeze, say, 5-7 mph., the plume of warm air will be displaced a little downwind. The weather type that will produce the strongest heat-island is one that combines light winds, sunshine by day, i.e. anticyclonic weather. In winter, this may become enhanced by changing the pattern of snow cover. If there is a light snowfall, the snow cover will not last long in the inner city.
Snow is cleared from roads and rapidly melts from rooftops.
The city will present its usual surface to the incoming solar radiation, absorbing a significant amount of solar radiation and warming up further. The surrounding countryside will still be snow covered and will thus fail to absorb incoming radiation to the same extent, enhancing the temperature difference between country and city. This was illustrated clearly by the light snowfall of 27 December 2000 when 1-3 cms. of snow fell in the counties around London. This rapidly cleared from much of inner London. On the following night, temperatures fell to around - 6 C in the outer suburbs and lower in the frost hollows beyond.