Which one is February and which May?
You may be surprised to find that the plotted chart on the left is for the 9th of May, whilst the one on the right is for the 25th in the record warm spell at the end of February  over 10 weeks earlier. Such are the vagaries of the British weather. Use the vertical slider to display a mix of plotted observations for each month. Forgive the fuzzy appearance of the images but its a problem with the plugin I am using and hopefully the author will respond and maybe fix it.