Welcome to the Spring weather forecast 2025, aimed at Reading & Berkshire though probably applicable to most of the south of England, as I talk quite broad brush.

I shall start with the usual caveat – seasonal forecasting can only be experimental, background signals can give an idea of what to expect, but notable events can override such signals.

It looks like we are about to have a sudden stratospheric warming event, which is annoying timing, both for the accuracy of this forecast and for the prospects of good spring weather.

This does mean that I’m less confident than normal – I’d rather be doing this forecast in two weeks time, and I may well do an updated version if the sudden stratospheric warming event happens (likely) and it upturns current expectations.

In any case, no seasonal forecast from any forecaster will be completely accurate, except if they get exceptionally lucky. My winter forecast was alright – both January and February were wetter than I expected, but high pressure was in control for much of February as I expected, just in a slightly different place. December’s forecast was pretty good. I wouldn’t give myself especially high marks.

Also I’d like to thank everyone that contributes, both in terms of comments on the Facebook posts and especially the photographs that are sent to me to use…the forecasts look much more boring without them.

And for this forecast, thanks to Donna for the cover photograph – a small donation to the charity of your choice will be made shortly.

Background Signals

Background signals tend to mean less in spring/summer, though the one overriding factor is the likely sudden stratospheric warming event.

Such events often (but not always) lead to high pressure blocks in positions that favour cold weather spreading down from the Arctic, or from Russia – so northerly or easterly winds.

Whilst a northerly flow will always be cooler/colder than normal at any time of year, easterly winds from around mid-April onwards can be warmer than normal, depending on the exact air source, and how much North Sea cloud is involved.

Effects from a sudden stratospheric warming (SWW) event tend to take 2-6 weeks to filter down into the troposphere (our level of the atmosphere).

Until the event has happened, and still it is possible that it is just a notable warming of the stratosphere and not an SSW, we can only talk in chances of something happening.

The other background signals include a weak La Niña and the QBO being in westerly phase, which should increase the chances of westerly flows. That said, these were also in affect during the winter, and we had reduced westerly flows compared to normal.

Conclusion? No idea.

March

Well let’s start with the bit I know – March will start sunny with overnight frost and/or fog, and temperatures will recover to a little above average. Something more showery likely for a time for the second week – mild or quite warm at first, possibly colder later.

Uncertainty increases notably for the second half. Something changeable broadly looks the theme, though with high pressure close by more often than not. Said high pressure more likely in milder positions, though brief cold snaps will remain possible, in the mix. Overnight frosts still possible. Some showers and occasional rain but overall probably more dry and sunny days, than showery days.

Overall I expect above-average temperatures, somewhat above-average sunshine and somewhat below-average rainfall.

Confidence level around 50% – pretty low compared to what I can normally feel.

April

Confidence really drops off a cliff now, due to the probable sudden stratospheric warming event, and the unknown outcomes – though outcomes more likely to favour cold flows than normal.

I was very confident of high pressure being in control for April until recently, but one effect of an SSW event can be for the Arctic air to go flooding south to our west, over the Atlantic, which then blows up large areas of low pressure – we saw this last winter where SSW events led to something milder and wetter.

But I’m going to stick to the more likely outcome, which is colder and drier weather with high pressure either to our north/north-west or west – allowing colder flows from the north or east for the first half of April.

Variable amounts of sunshine and cloud from day to day, some showers likely – some sleet/snow would be possible. Colder than normal conditions more likely, but brief quite warm spells could be mixed in too. Overnight frosts still possible.

I’d assume high pressure to continue to be fairly close by for the latter half of April, again some changeable conditions, some showers possible some days, though temperatures more likely to be average or above-average.

Overall I expect around average temperatures, slightly above-average sunshine and slightly below-average rainfall.

Confidence level just 20%. Damn that sudden stratospheric warming event.

May

By this point the effects of the SSW event (assuming it happened and assuming it was impactful) lessen. Should high pressure be to our north, the resulting easterly winds would be warm by this point – though should it be to our west, northerly flows still chilly.

My best guess is that high pressure will be to our north to allow easterly flows, so often warm and sunny, though not always, for the start of May. Cloud spilling in from the North Sea overnight and leading to cloudy mornings – or possibly cool and cloudy days, is possible, in such a set-up.

As the month goes on, heavy showers will tend to increase in prominence across the south of England, with low pressure tending to be close by to our south, over France. Potential for some decent thunderstorms (or indecent if you don’t care for them). Likely still warm/very warm with sunny spells.

Overall I expect above-average temperatures, slightly above-average sunshine amounts and an average number of days of rain – rainfall totals could be anything, depending on how heavy any downpours are.

Confidence level of 40%.

Summary And Early Summer Thoughts

Yikes…lots of uncertainty. May holds the most promise for those looking out for sunshine and warmth, though I do expect all 3 months to be sunnier than normal. Anything outstanding wet looks unlikely, though who knows what the effect of the SSW will be – all I can talk about is more likely outcomes for now.

I wish the SSW event happened two weeks earlier, or I did my forecast two weeks later. Alas. Maybe I’ll do an updated version in two weeks but I doubt I’ll have time.

Early summer thoughts are for a fairly hot first half/two-thirds of summer, though I’d still expect some heavy showers at times – early signals for August are looking notably wet. But that is a very, very, very long way away.

And that is your Spring Weather Forecast 2025. Thoughts?!