Because by checking the weather you might be able to forecast the weather for the next month and a half!
"Candlemas" is a Christian holiday to celebrate the Presentation of Jesus at the Temple, that celebrates an early episode in the life of Jesus that occurs on February the 2nd.
Traditionally the Western term "Candlemas" (or Candle Mass) referred to the practice undertaken on February the 2nd when a priest would bless beeswax candles for use throughout the year.
In Pagan times the Romans had dedicated the month of February to the infernal gods. The time when Pluto stole Proserpine, and her mother Ceres sought her in the night with lighted candles that became the stars. At the beginning of February there were many processions where people walked about the Rome with lighted candles.
The 2nd has also become known as Groundhog Day, the day on which, according to the Germans, the Groundhog peeps out of his winter quarters and if he sees his shadow he pops back for another six weeks nap, but if the day be cloudy he remains out, as the weather is to be moderate.
In the United Kingdom, good weather at Candlemas is taken to indicate severe winter weather later:
"If Candlemas Day is clear and bright, winter will have another bite".
"If Candlemas Day brings cloud and rain, winter is gone and will not come again".
There is some evidence for the latter poem. If the winter weather fronts from the east dominate then colder and brighter days will be experienced in the UK.
However if the Atlantic climate associated with spring weather is dominant then warmer and wetter days will be experienced.
The first week of February is about half way through winter so this dominance may well predict the weather for the rest of Winter.
Of course this is not an exact science and depends on your longitude and latitude but it's an interesting experiment to try for yourself and test if this superstition is true for yourself.