My trial lesson was pretty similar, the instructor told me that it could be quite bumpy and was i ok with that, and explained that if i felt uncomfy then we would come back straight away, i really enjoyed it thou and the weather didnt bother me, sorry that it made u feel a bit sick but that could also be nerves and excitment for your first lesson,
just look forward to the next one and hopefully if you get better conditions it will be more fun for u