In reply to David Hooper:
Ha ha
Definitely not shorts and t-shirt weather.
Since it's a month away there's no telling what weather you may encounter. It could be mild and wet, it could be mild and dry, it could be cold and snowy, it could be cold and frosty but no snow.
Be prepared to take your winter and spring weather gear and axes and crampons and keep an eye on the forecasts nearer the time.
This time last year I was rock climbing in Snowdonia. This year ice climbing.