How is it possible that hail struck the barley? There was a month between Makos, so this was in Teves. Eretz Yisrael ripens its Peros quickly, and the first barley ripens around the time of Pesach!
Moshav Zekenim: Tehilim 78 records some of the Makos in a different order. However, this is not an answer, for R. Yehudah's Siman for the Makos shows that they were in the order that the Torah says, and we follow him against R. Shimon (who argues)!
Perhaps barley is planted in Egypt earlier than in Eretz Yisrael. Even though they are close to each other, their climates differ; Eretz Yisrael relies on rain, and Egypt, on the Nile. (PF)