Shannon has a relatively mild climate year-round thanks to the moderating effects of the nearby Atlantic. Tourists will probably find it more pleasant to visit during the summer, as the temperatures are quite cool in comparison with most of North America or Europe. The climate can get very wet, though, as Atlantic storms sometimes make their way up the coast. However, Shannon lies in a fairly protected region of Ireland, so it usually suffers no more than some strong winds and heavy rainfall.

The Atlantic storms generally come in the late autumn and winter (another good reason to visit during the summer). During the winter, temperatures only go below freezing a few days during the year. There may, however, be some snow or hail in addition to the frequent rain, but these usually come in short bursts and melt away quickly.

Over the course of the year, there is very little temperature fluctuation. Averages range from about 42°F (6°C) in the middle of winter to 60°F (16°C) during the months of July and August. Sunshine in this part of the country, however, is rather rare, with the sunniest months being May and June. Even during these months, however, Ireland’s wet climate means that Shannon still sees a good deal of rain, on the order of 2.5 inches (63mm) per month. This rises to nearly 4 inches (100mm) during the winter to give an annual precipitation level of about 36 inches (92.5cm).