Celtic Festival of the first fruits & the ripening corn.
"Lammas" is a Saxon word meaning "loaf festival" as it celebrated the harvesting of the first corn for baking into bread. It was traditionally a time when communities would gather together to celebrate their harvest with lots of feasting and drinking. It was also one of the four ancient Celtic Fire Festivals.
If you'd like to celebrate Lammas, the nicest way to do it would be to invite friends and family for a picnic and bonfire. The food should reflect the season and feature lots of fresh local fruits and, of course, the all-important bread. (You could prepare for the picnic by picking your own fruit at somewhere like Sharnfold Farm.) If you want to be really authentic, you will need to find a genuine corn dolly to take pride of place on the table (or picnic rug) where she can represent the spirit of the harvest. Truly pagan types can then keep her until the Spring, when they should plant her in the garden to ensure a bountiful supply of good things next year.
Keep an eye on the weather over the next few days, too. There is an old country saying: "If the first week of August be warm, then the winter will be white and long".