Is St Hilary’s day the coldest day of the year?

Figure 1 – Courtesy of Wikipedia (By Chordboard)

In weather folklore there is a widespread belief that St Hilary’s day, which falls on the 13th of January, is the coldest day of the year. But is this true? We sent our meteorological reporter xmetman out to check the CET series, in an attempt to find the truth. And what did he conclude after analysing the daily CET series back to 1878? Well, the short answer to the question is no, the 13th of January is not statistically the coldest day of the year in the CET series, it’s close, I make the mean minimum for that day is 0.96°C, but another Saint’s day, St Valentines on the 14th of February is, with a mean minimum of 0.67°C. The chance of frost on the 13th of January in the 137 year record since 1879 is 37.1%, whilst the chance of frost on the 14th of February is 40.3% the highest frequency of frost in the whole year. It’s also interesting to see that the dip in temperature in the lower graph (fig 2), ties in quite nicely with the first of Alexander Buchan’s cold spell s (February 7th to 14th) that he found in 1867. I think with the weather turning milder, a frost this year, might be pushing it a bit in Central England tonight.

Figure 2 – Data courtesy of the Met Office


About xmetman

I am an exmetman who is passionate about all things to do with weather and climate. I have no axe to grind, and am continually upsetting people on both sides of the global warming debate with the articles that I publish, hell, I'm even banned from commenting on the Met Office's own blog! What I do fight for is the freeing up of climate, observational and forecast data collected and created on our behalf by the Meteorological Office.
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