Do I really need rain boots?

No. Unless you are hiking in the countryside, rubber rain boots are bulky and unnecessary for city walking. Comfortable, water-resistant leather boots will suffice.

Is it ever too rainy to sightsee?

Rarely. Londoners go about their day regardless of the drizzle. If it is pouring, duck into a museum or a local pub until the intensity drops.

How to pack rain gear for a trip to London

Pack a lightweight, breathable, and fully waterproof trench or rain shell rather than an umbrella. London rain is usually a persistent mist rather than a heavy storm, so prioritize gear that layers easily and dries quickly.

Ditch the full-sized umbrella. Don't waste luggage space on a heavy umbrella. If you must have one, bring a compact, collapsible version that fits in a side pocket. London wind often destroys cheap, flimsy umbrellas, so buy a sturdy one locally if the forecast looks dire.
Select a technical shell. Look for a jacket with a high waterproof rating (at least 10,000mm) and taped seams. Avoid heavy waxed cotton unless you are strictly doing outdoor walking, as it stays damp and heavy for hours.
Prioritize footwear. Pack one pair of comfortable, water-resistant leather boots. Canvas shoes will soak through in minutes on wet cobblestones; if you wear sneakers, treat them with a waterproof spray at least 48 hours before you leave.
Use the layering system. London weather changes every 30 minutes. Wear a moisture-wicking base layer, a merino wool sweater, and keep your waterproof shell on top. This allows you to vent heat quickly when you enter the Underground.

Do I really need rain boots?: No. Unless you are hiking in the countryside, rubber rain boots are bulky and unnecessary for city walking. Comfortable, water-resistant leather boots will suffice.
Is it ever too rainy to sightsee?: Rarely. Londoners go about their day regardless of the drizzle. If it is pouring, duck into a museum or a local pub until the intensity drops.