Allergies. An allergy is a broad category describing any time your immune system reacts differently than a normal person’s immune system would react when exposed to something. Symptoms can range from undetectable to extreme and constant, depending on the specifics of the allergy. Weather can play a huge role in allergies and their symptoms during all four seasons of the year. Some people are triggered by rain, others by dry weather. Heat triggers some and cold triggers others. Each of the four season changes can bring new changes in allergy symptoms: