Maybe there's one less worry about measures of happiness

Measures of happiness or subjective wellbeing essentially come down to responses to a question like: "Overall, how satisfied are you with your life at the moment?" There are a number of problems with that sort of question, not least of which is that it can be influenced by recent and usually unobserved factors such as the weather. That is, if the day is sunny and warm (but not too hot) you probably feel a bit happier than on a cold, rainy day, and most studies would not be able to control for the effect of the weather on your happiness. So that would lead to omitted variable bias in any analysis of the factors associated with happiness.

Which makes this recent paper from the journal The Manchester School (sorry I don't see an ungated version anywhere) by Franz Buscha (University of Westminster) potentially quite important. In the paper, Buscha uses data from the British Household Panel Survey, which allowed him to identify the day and location of each interview, and therefore match weather data to each observation. Past studies have sometimes shown relationships between weather and various measures of subjective wellbeing, but in this case the results were very weak:

Results suggest that, in general, there is little correlation between measures of well-being and the weather. None of the correlation coefficients exceed an absolute value of 0.05, which suggests that, at least in a descriptive setting, there is little interaction between weather and well-being responses.

When using more robust regression methods:

...results suggest that the causal effect of weather on individual measures of well-being is generally statistically insignificant. 

There were some weak statistically significant relationships, but the size of the effects were tiny. So, overall this suggests that we may have little to worry about in terms of whether the weather is causing problems for happiness studies. However, this study was in Britain, and most interviews were in the autumn, and the weather in Britain in autumn is typically rubbish (according to the paper "[t]he ‘average autumn day’ ... includes a gentle breeze, some low-intensity rainfall, moderate temperatures and roughly half sunshine/half cloudy weather"). Perhaps a further study in a more varied (and nicer) climate is required?