Your specific request is a bit at odds with the traditional role most of these Saints have played.
Saint Sebald is the patron Saint against cold weather.
Medard is considered the patron Saint against bad weather/for rain.
Interestingly, he may have been the first to celebrate a version of Groundhog Day:
Legend has it that if it rains on his feast day, the next 40 days will be wet; if the weather is good, the next 40 will be fine as well.
Agricola of Avignon is the patron Saint for rain and good weather.
There is Clare of Assisi, but I couldn’t find anything in her biography to indicate why she is associated with weather, or any specificity as to what weather.
More promising is Eurosia, who according to the link is apparently the Saint for furious hail, but unfortunately also of frightful waters.