Weather is probably a major factor when you plan your trip to Shell, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually September and October with an average temp of 65°F, while the coldest months are July and August with an average of 64°F. The rainiest months in Shell are April, May, June, and March, with each month seeing an average of 17 inches of rainfall.