Allison wani hadari ne mai zafi wanda ya lalata kudu maso gabashin Texas a watan Yunin 2001 na lokacin guguwar Atlantic. Misali mai ban mamaki na "tasirin teku mai launin ruwan kasa", Allison ya daɗe sosai don guguwar Yuni, ya kasance mai zafi ko na wurare masu zafi na tsawon kwanaki 15, mafi yawan lokacin da guguwar ta kasance a kan ƙasa ta zubar da ruwan sama mai yawa. Guguwar ta samo asali ne daga raƙuman ruwa mai zafi a arewacin Gulf of Mexico a ranar 4 ga Yuni, 2001, kuma ta buge gabar tekun Texas ba da daɗewa ba bayan haka. Ya koma arewacin jihar, ya koma kudu, kuma ya sake shiga Tekun Mexico. Guguwar ta ci gaba zuwa gabas ta arewa maso gabas, ta sauka a Louisiana, sannan ta motsa zuwa kudu maso gabashin Amurka da Mid-Atlantic Texas.
Louisiana da kuma kudu maso gabashin Pennsylvania