The duration of daylight has a sinusoidal relationship to time of year, with increasing amplitude as you move away from the equator towards the poles. This is the main 'forcing function' determining temperature. If you plot the frequency distribution for a sine curve, it is close to uniform, with fairly steeply shelving shoulders. Superimpose random variation, and you would expect to get an approximately Gaussian distribution - like we get here in the UK.
So - why do some places have a fairly abrupt shift between a colder and a warmer season? I'm not thinking of tropical places with a wet and a dry season, but places well away from the equator. See for example
which shows a clear bimodal pattern for maximum daily temperature in Yakutsk. Can anyone explain this please? It is said that nature abhors a vacuum, and one manifestation of this is that bimodal distributions tend to arise only as mixtures, e.g. log testosterone levels in adults. So, why do Yakutsk and many other places show this seemingly unnatural pattern?