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Last update: 21:00, 5 Oct 2026
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Sunbury-on-Thames sits on a bend of the Thames in Surrey, with Sunbury Lock and its weir on the river and Kempton Park Racecourse close by on the Middlesex bank. Rain on the upper Thames catchment can keep the river rising at the lock long after the sky over the town has cleared. Open a Sunbury-on-Thames rain radar and the picture changes, because hyperlocal radar shows the shower's actual path rather than a citywide estimate.
Rain falling well upstream on the Thames catchment takes time to reach Sunbury, so the river at the lock and weir can keep rising for a day or more after the rain overhead has stopped. Frontal rain arrives from the south-west, but summer storms are the real forecasting problem. Heat trapped over the city and the Chilterns and North Downs steer and trigger cells, and drainage can be overwhelmed within minutes by a storm that a forecast rated as a chance of showers.
Over Sunbury-on-Thames, England, RainViewer's radar map runs on live Met Office data, with each scan landing on the map within minutes. The live map gives a hyperlocal read on whether a shower is still over Walton or already at the lock, which a forecast for Sunbury-on-Thames cannot tell you.
Winter rain on the upper Thames raises the river through Sunbury, and the towpath by the lock is the first ground to go under water. Between October and January, one frontal band follows another, and named storms bring wind alongside the rain. The Thames and its tributaries respond to all that repeated rain by rising, with roads, rail lines and low-lying streets typically the first to be hit.
Cold showers, hail and sun alternate, and forecasts are least reliable because the showers are small and fast. Spring races, park events and weekend sport are the most exposed. Cold spring showers cross Surrey quickly, and a walk along the weir is the plan most often cut short.
From May to September, heat builds over the built-up area until thunderstorms break, producing short, intense rain that can flood roads and stations within minutes. Festivals, tennis and open-air events hinge on which way a storm cell tracks, which radar reveals before the sky itself does. Race days at Kempton Park and summer evenings by the lock depend on the gaps between short showers off the Thames valley.
Racegoers walking from Sunbury station to Kempton Park Racecourse cross open ground with little shelter, and rain changes the going underfoot. Watch the shower approach and time the walk to the gate.
The towpath by Sunbury Lock and the weir sits right beside the Thames and floods readily after rain upstream. Check the radar before setting out along the river.
Anglers on the riverbank near the lock have almost no cover once a shower starts. See whether the cell will pass before casting a line.
The A308 along the river and the M3 near Sunbury slow fast in heavy rain, and spray builds on the open stretches. A look at the radar settles whether to go now or hold off.
RainViewer shows UK precipitation using data from the Met Office, the national weather service, which runs a network of C-band dual-polarization weather radars. The Met Office network also feeds the European OPERA composite, and the RainViewer map refreshes with each new scan, about every 5 minutes. From Sunbury-on-Thames the map also covers Walton-on-Thames, Shepperton and Staines-upon-Thames.
Rain on the going at Kempton Park Racecourse can change the ground within an hour and soak the walk from the car parks to the stands. Racegoers and stewards both watch the sky between races. RainViewer shows the shower crossing the Thames valley before it reaches the course.
Yes, heavy rain slows the A308 along the river and the roads near the M3 through Sunbury-on-Thames, and spray builds fast on the open stretches. Look at the radar before you join the road. RainViewer shows whether the cell is still to come or has already gone through.
Yes, the Thames can flood the towpath and low ground near Sunbury Lock after heavy rain on the upper catchment, and the river can keep rising for a day or more after the rain has stopped. The town centre on higher ground stays largely dry. Check the map to see if more rain is falling upstream.
May to September is the best window to visit Sunbury-on-Thames, with the lock, the towpath and Kempton Park at their most pleasant. Showers are shorter in summer but the Thames valley still catches its share. Check the radar in the morning and plan the outdoor part of the day around the gap.
The towpath and weir at Sunbury Lock sit right beside the river and flood easily, while the town centre a little further back on higher ground can stay dry through the same wet spell. RainViewer draws each shower where it actually is, which is why a look at Sunbury Lock by the Thames and the town centre set back from the river can give different answers.
A forecast for Sunbury-on-Thames predicts rain with a probability, while RainViewer shows the rain the Met Office radar is measuring right now, with a new frame about every 5 minutes. Dual-polarization radar from the Met Office distinguishes heavy convective downpours from ordinary frontal rain, a distinction that matters in London because it is the convective storms that overwhelm underpasses and flood stations. That hyperlocal radar view tells you what is happening on your street.
Set a rain alert on Sunbury Lock or Kempton Park and RainViewer warns you before rain arrives, with a hyperlocal view down to street level. That lets you time a riverside walk or a day at the races. The 2-hour forecast in 5-minute slices shows the next gap, and saved locations track Walton-on-Thames and Shepperton together.
A walk by Sunbury Lock and a day at Kempton Park both depend on a dry gap, and RainViewer shows the next one.
Rain in Sunbury-on-Thames arrives in bands from the south-west, and summer storms can appear within minutes.
Your phone forecast says rain in Sunbury-on-Thames this afternoon. RainViewer's live hyperlocal radar shows the cell still over Walton with the lock still dry, and that decides whether the walk starts now.
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Slice the next two hours into 5-minute steps and pick the gap for the walk along the towpath.
An alert on Sunbury Lock arrives while the rain is still on its way, and that decides whether to walk the towpath or take the road.
In Sunbury-on-Thames the wet weather tends to come from the south-west, and the arrows show the track of every shower.
Scroll back over the upper Thames catchment above Sunbury to see what actually fell overnight.
Track Sunbury Lock, Kempton Park and Walton-on-Thames together and compare which one is dry.