From the NHS website about hay fever:
"Pollens are released in the early morning. As the air warms up, they get carried up into the air above our heads. As evening comes and the air cools down, the pollen comes back down.
This means symptoms are usually worse first thing in the morning and in the evening, particularly on days that have been warm and sunny"
http://www.nhs.uk/Livewell/hayfever/Pages/Weatherandayfever.aspx
There are fairly few plants that produce pollen this time of year (but there are certainly some). Anyway, irrespective of whether it's pollen or not, there's almost definitely something in the air which you're allergic to, which means that you need to seek out an antihistamine treatment.
Head to your nearest pharmacy and ask for loratadine tablets. (Loratadine is the active ingredient in well-known, and often rather expensive, hay fever tablets. However if you just ask for 'loratadine' you should be offered non-branded [generic] tablets at a fraction of the cost. I recommend Co-op pharmacies as a particularly cheap source).