TORRENTIAL downpours were liberally scattered across the country throughout May. Not so far away, parts of Leeds were flooded after about 40mm (1.6ins) of rain fell within a couple of hours on the 3rd. The storms conjured up some large hail as well - the size of golf balls near Reading. There were many reports of whirlwinds or small tornadoes, too.

Such events are not exceptional for late spring. With the sun progressing towards its maximum strength and the remnants of very cold air from winter floating around in the upper atmosphere, May always has the potential to create spectacular weather.

Our region appears to have missed the worst of the showers. They were still frequent here at times and often accompanied by hail and thunder, even if they were not especially noteworthy. Consequently, it was generally quite a dry month with about two-thirds to threequarters of anticipated rainfall. One or two places that did catch several of the heavier deluges did just about approach their usual total for the month.

The five days with hail during the month here at Carlton in Cleveland, near Stokesley, was the most that I've registered in any May in my 22 years of observations. Additionally, the five days on which I heard thunder equalled my record for May, previously achieved in 1988.

Overall, temperatures were about average or fractionally above, particularly by day, but a shade below at night. Even so, it was widely the coolest May for eight years, emphasising the sustained warming trend in recent years. I observed no less than ten ground frosts at Carlton, matching the most for the month, noted in three other Mays - 1984, 1996 and 1997.

The first bank holiday weekend got the month off to a very warm though mainly cloudy start with a humid southerly flow covering Britain. However, the area of high pressure over the near Continent responsible for this pulled away east, allowing a depression in the Atlantic to head north-east towards us.

A few showers broke out on both the Sunday and Monday, becoming widespread and thundery around midday on the Tuesday as the low trundled across our area. Behind it, winds veered into the north and temperatures plummeted. After rising to 20C (68F) in many spots on the Monday, they struggled to 10C (50F) on the Wednesday.

Then, with another high cell establishing itself to the south-west of the British Isles, a north-westerly spell commenced. This was not quite so cool but there were still a few showers. Towards the second weekend, winds gradually became northerly again, dragging down even colder air aloft from the Arctic. As a result, the showers pepped up again with hail and thunder reported widely and sleet, too, in some. The mercury once more toiled to reach double figures on the celsius scale.

After this, high pressure nosed north-eastwards across Scotland turning the breeze into the east and drawing in dry but still very chilly air from southern Scandinavia. The showers quickly died out and the cloud broke up well. With plenty of sunshine by day, temperatures recovered to nearer typical values, but with the clear skies at night, ground frosts were common with the odd local air frost.

Sunday, May 15, saw winds back to the south-west briefly as a frontal system worked its way south-east. By the Wednesday though, milder air had returned heralding an unsettled period that was to last until the end of the month. A series of depressions marched north-east across or close to northern Britain, one every few days or so. Frontal systems brought small amounts of rain in the lee of the Pennines but, between them, showers formed readily and some were beefy, with hail and thunder once more.

At least with the airstream originating from a south-westerly quarter, temperatures picked up to above the norm. A mini-heatwave affected the South-East, where they peaked at an incredible 32C (90F) in London on May 27, the warmest in the country for nearly two years and the hottest May day there for 60 years.

We reached a modest but much more comfortable 19C (66F) or thereabouts, as on other days during the last week. In most places, however, it failed to top the highest of the month that occurred on Monday the 2nd. We virtually said goodbye to the risk of frost at night, too, though there was a further touch in hollows prone to it early on Monday, May 30.

It had become mostly dry as well by Wednesday the 25th and the final bank holiday was fine, though the Saturday was very breezy. This provided a stern test of strength for the trees in their fresh cloaks of new leaves.

The spring was slightly milder than usual, by about 0.3C (0.5F), though the chilliest for four years. Rainfall was near normal despite the wet April.

May temperatures and rainfall at Carlton in Cleveland

Mean max 15.2C, 59F (+0.2C, +0.4F)

Mean min 6.1C, 43F (-0.4C, -0.8F)

Highest max 20.4C, 68.5F, 2nd

Lowest min -0.9C, 30.5F, 11th

Total rainfall 38mm, 1.5ins (-4mm, -0.15ins)

Wettest day 9mm, 0.35ins, 3rd

No of rain days, with 0.2mm (0.01ins) or more 15 (+2)

(Figures in brackets show the difference from the 21-year mean, 1984-2004)