Your experience of England in September? Weather? Clothing? Etc.?

High 60’s. Dress in layers. You could bring shorts but should also have long pants, long sleeve fleece and a waterproof coat.

When you say “ beauty of the area,” are you commenting about The Cotswolds?

Over decades of UK visits I’ve traveled in July, October, November, December and February.
July was the warmest. February the coldest.

I’m a carry on traveler no matter what time of the year.

One absolute; forget the flip flops.

We were there for about those same dates this past September. The first 10 days were in London, and temps were in the upper 60s and low 70s. We wore short sleeves during the day, and I wore a light cardigan in the evening; my husband was comfortable without an outer covering. Then we traveled to Bath, where it was still quite warm. We didn't notice any cooling until we began traveling to the Cotswolds and Wales, but this coincided with the weather turning from lovely sunny days to several cooler rainy ones. Still, temps were in the lower to mid 60s in the daytime, and high 50s in the evening, as I remember. We were still comfortable in short sleeves in the daytime, and a cardigan in the evening, with the addition of an unlined rain jacket when it was needed. I should say that we are from the Pacific Northwest, so if you are from a warmer climate, you might find the ambient temps chillier than we did. For us, these were pleasant autumn days.

Last 2 weeks of September, three years ago: pleasant during the day, but a jacket was needed at night. Medium-weight jacket, not a super-light windbreaker, but not a heavy parka, either.

As for beauty outside of London, the gardens at Hampton Court were pretty much done for the season. There were still some green plants and stems, but the flowers from summer were all gone. Our B&B provided umbrellas the one night we needed them, and for the one day it looked like it might rain, but never did.

Who knows with our weather! You may be lucky and get glorious wall to wall sunshine and warm temperatures (an Indian Summer). You may get a few cloudy and rainy days, although Septemebr is traditionally one of the drier months... This website may give some help.

Claudia is spot on with her advice. A rainproof jacket is a lot more use than an umbrella.

You are very unlikely to get snow and ice. Other than that, anything is possible - heatwave to lots of rain to a drought.

Wear layers. Bring a waterproof jacket and shoes.

Beauty of the area?? What area? There should still be some colour in the gardens, although they will be past their best. You are a bit early for autumn tree colour.

We did a four week drive tour of England and South Wales in October 2017 and the weather was very nice. Very little rain and it didn't really get chilly until the end of October.

Weather will still be reasonably mild. You won’t need to bring a big coat. I’d second layers. If we’re going in a U.K. holiday at any time of year we always take fleeces, waterproofs inc waterproof trousers (not for the city!), waterproof shoes and a lightweight puffa. Basically we know it could rain and we’re going to be outside regardless.

I have been several times in September and October, the latest was 2022. The weather tends to be wonderful with occasional rainy days. I usually pack for a week no matter how long I expect to be traveling. The only difference in these months is I pack more layering options. I have a great 'longish' rain jacket which is large enough for a sweater underneath and I pack a pair of lightweight gloves & head covering.

Weather will still be reasonably mild
Unless it isn’t.

It is highly unlikely you would feel the need for a proper winter coat in September in southern England. I certainly never get mine out until mid October. Layers are your friend. Prepare for rain and the damp air can feel chilly so as I said a light weight puffa is always useful. Uniqlo do great ones that pack up really small and light. I have one that I keep in my backpack and put on under a waterproof or over a fleece for an extra layer if necessary. You’re unlikely to need it if you’re walking around but if you end up sitting or standing outside you might be grateful for it.

You'll really enjoy the sights on Rick's Best of England (or as the guides call it, Best of Britain since it includes Wales!). There are lots of varied sights and a bit of outdoor time. I'll vote for a waterproof rain jacket with hood as well since your route will go from Bath to the Cotswolds, to Wales to the Lake District with a finish in York and London.

Here is a link to my Trip Report from a similar time frame in 2015 so it's older but still fairly relevant. I see I took 3 cardigans as I was doing 2 back to back tours and extending in to October in Paris so it got a little chilly toward the end for me. Seven years later would have me packing even lighter than I did then.

https://community.ricksteves.com/travel-forum/tours/trip-tour-report-for-best-of-england-paris-hof

I always sink wash so I make sure all my clothing will dry overnight. Others don't like to do that so there is an opportunity to do laundry or have it done in Keswick (Lake District).

I'm glad you are going early to Bath. I always find a lot to see there and you'll just have 1 full day in Bath while the other full day is devoted to visiting Wells and Glastonbury. Are either of you Jane Austen fans? There is a JA festival in September but it looks like it starts Sept 8 this year.

Time in London is ALWAYS a good thing!

We visited the last 2 weeks of September and first week of October just before the pandemic struck. We found the wind ferocious at Stonehenge both times we were there so I'd recommend something hooded to cover the ears. The wind was also fierce at Castlerigg Stone Circle which made the cool misty fine rain feel really cold. We had a short walk at Pen y Pass in Snowdonia where we were drenched in a cold fine mist. A waterproof jacket will be needed. Most other locations were comfortable high 50's to low 60's with stretches of pleasant sun and minor misty showers that dispersed as quickly as they appeared. I wish our landscape in southeast Michigan could be as lush.

Well, I don’t know what part of the world you live in and therefore, not sure how tolerant you are to heat, rain, cold, etc. However, I was in London this year in mid-September and there were mostly sunny days, but one quite rainy day. I live in the Seattle neighborhood which has very temperate weather and very close to what Scotland and England has. 2022 winter in Seattle has been odd though with frozen roads last week. So, like others here, I recommend thin layers and a water resistant/waterproof jacket with a hood and wind breaking properties. Have fun on your tour. RS does a good job with his tours.

You can keep checking the weather forecast online up to the minute of departure, and change your packing accordingly.

I’ve been twice in September, early to mid-month—stayed in London, also went to Brighton and generally had warm weather, wore sleeveless tops, or a bit of rain and used a light jacket. It’s ideal weather for me and my preferred time to visit.

September is often nicer than August

You can keep checking the weather forecast online up to the minute of departure, and change your packing accordingly.

Trying to forecast the British weather is notoriously difficult particularly if winds are coming from a westerly direction, even the MET Office (the UK's meteorlogical agency) frequently get the forecast wrong right up to a day in advance so I would recommend packing for warmth but bring a waterproof jacket/coat and some light layers just in case.

We’ve generally had good weather in September with occasional rain. On our recent trip it rained the entire time we were in the Lake District, but the weather was great on the eastern coast in the Alnwick area. Weather in the UK is always a mixed bag and one needs to be prepared for anything.

There is sadly no rhyme or reason to our weather. Pack for all seasons!

Thank you all. Very helpful comments.

Comment about a rain jacket, make sure you have one with a hood attached. I have one with a hood and one without. We didn't have any rain in Southern England in September this year, but in 2018 we had 1.5 days of constant downpour-more rain and constant that I'm not used to at home. Without an attached hood, the rain would have been pouring down my back inside the jacket. At home, the hoodless one is OK in most situations and I never would have thought about it until I experienced London rain.