A weak sneeze indicates that a tiny bit of irritant may be tickling you. A strong sneeze means a big irritant. Examine your tissue for discharge. If not, the sneeze was probably caused by an environmental irritant or bright light, which stimulates the optic nerve. Look at the color and consistency of the discharge if you did expel.
Clear discharge can mean an allergy or the beginning of a cold or flu.
Runny, watery discharge points to allergies or a cold draining. Repeated short, weak sneezes without significant discharge indicate allergies. Check the pollen and mold spore count. If those levels are high, your sneezes may be allergy induced. Think back on what you did earlier in the day.