How is it possible that hail struck the barley? There was a month between Makos, so Barad took place in Teives; and the Peiros of Eretz Yisrael ripen earlier. Moreover, the first barley only ripens around Pesach-time?
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)
Oznayim la'Torah #1: According to the Midrash ha'Gadol. Makas Choshech lasted only three days and Makas be'Choros, only one moment. 1
Oznayim la'Torah #2 (citing the Rash in Kil'ayim, 5:7): Sometimes "Aviv" pertains to corn that has not yet grown one third of its full height. 2
Oznayim la'Torah: It seems that the corn ripens in Egypt in Adar and in Eretz Yisrael, in Nisan
Onayim la'Torah: IN which case, Makas Arbeh took place in Adar. And acording to the Ramban in Bo, Makas Barad took place in Adar and the last three Makos, in Nisan