From the Met office:
UK Outlook for Saturday 3 Apr 2010 to Monday 12 Apr 2010:
The weather is likely to remain unsettled throughout the Easter weekend, with a mixture of sunny spells and blustery showers expected. There is also a risk of snow falling, mainly over northern hills but possibly elsewhere at times. Some drier and brighter periods are also likely, mainly toward the end of the Easter weekend and into the start of the following week. These may become most widespread in southern areas which may become drier and more settled. However, the generally unsettled picture is likely to continue so further showers or rain are likely and it will be windy in places. Temperatures are expected to be below average in most places at first but could recover to be closer to average by the second weekend of April.
They are predicting heavy rain for Friday day time
Bad news for Herne Hill Good Friday Meet.