Seasonal allergies tend to act up amidst warmer weather as pollen runs rampant and our lawns continue to be manicured, releasing allergens into the air. When our body comes into contact with an allergen, we release histamines and other pro-inflammatory mediators. The runny nose and water eyes you have are your body trying to rid itself of the allergens. The stuffy nose is from your mucous membranes becoming inflamed and swelling.