Comprising the 'Ice Saints' of St Pancras, Servatius and Mamertus, the 12th, 13th and 14th of May are said to be often chilly. But however you view this old folklore, this year seems to be bucking the trend, as it becomes warmer over the next few days. It'll also be turning somewhat humid over the weekend, potentially triggering a few heavy showers and maybe thunderstorms in southern parts overnight Saturday that could move north into other parts of the country on Sunday.
Today, pressure is low to the North and high to the South, leaving a brisk South Westerly airflow across all parts.
Atlantic systems that gave some rain overnight across the northern half of the country have now largely cleared but will still have some patchy drizzle across the North of England. This'll soon clear to leave a fine, dry day for most, the exception being the North and West of Scotland, where showers that may be heavy towards Highland will keep going. While cloud amounts will vary, most parts will see a fair amount of sunshine today, with the best of this in the East and South.
A South West wind will be fresh and blustery, especially in the North, giving gale-force gusts across Highland and the Northern Isles, restricting temperatures to no more than 10 to 14C. It'll be warmer than yesterday for most, as 17 to 21C will be the norm, with 22 or 23C likely over more sheltered parts of East Anglia and the South East where it may begin to feel a little on the humid side later.
Northern Scotland continues to see some rain or showers after dark, but as pressure slowly builds from the South, it'll be a dry evening for most. There'll be some further sunshine to end the day, followed by clear spells overnight. A South Westerly wind will decrease to become light in central and southern parts, where some rural areas could see a few mist or fog patches developing towards dawn. It'll be a mild night, though, with the lowest temperatures mainly in the range of 8 to 12C.
For most, Saturday will be fine with lots of sunshine once patchy mist, fog and any low cloud that has formed overnight clears. It'll become warm, even very warm for some in lighter breezes, the only exception being the far North where a South Westerly breeze will bring cloud and some light rain or drizzle, but even here, the weather should improve. It continues mainly dry, but with the sunshine turning hazy in central and southern parts, which could 'trigger' the odd sharp shower in the far South and South-West towards evening. Top temperatures 18 to 22C, maybe 23 locally 24C in the sunnier parts of the East and South, but only 13 to 16C in the far North and North West.
It continues mostly dry in the North in a somewhat humid evening and night with clear spells. It turns misty, and a few fog patches may form in rural areas towards dawn with light winds. There's the threat of a few sharp showers and thunderstorms moving up from France into central and southern parts, although the extent of this remains uncertain at present. It'll turn misty in a North Easterly breeze with patches of very low cloud perhaps drifting onto some North Sea shorelines making it grey here by dawn. On a mild night, though, temperatures shouldn't fall below 8 to 11C in the North and 12 to 14C further South.