Portland claims to be the UK's premier sport climbing destination, and with its generally warm and sunny climate and enormous selection of well-bolted routes it can probably justify that claim. Almost all of the routes have been recently and sensibly bolted, and there's plenty to go at for climbers of all grades. Although some traditional routes snake their way in between the bolted lines, you can happily get away without taking a trad rack.
For more specific information, comprehensive details can be found in UKClimbing's climbing database:
Weather forecasts for Portland.