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How did the 1815 eruption of Mount Tambora affect weather in 1816?

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Line graph showing estimated temperature variations from 1000 to 2000 CE for the Northern Hemisphere and central England, with three lines representing different data sources. The chart highlights the medieval warm period around 1100-1300 and the Little Ice Age from about 1500 to 1850, followed by a sharp temperature rise in the late 20th century. Temperature is shown as deviations from the 1961-1990 average. — Little Ice Age Estimates of temperature variations for the Northern Hemisphere and central England from 1000 to 2000 ce.

The 1815 eruption of Mount Tambora was the largest volcanic event in recorded history, expelling massive quantities of ash and sulfur into the atmosphere. These materials formed aerosol layers in the stratosphere that reflected sunlight, preventing it from reaching Earth's surface and reducing the average global temperature by as much as 3 °C (5.4 °F).12

This cooling effect led to the "year without a summer" in 1816. In regions as distant as western Europe and eastern North America, the weather was characterized by:13

Sporadic extreme conditions: Heavy snow and killing frost occurred throughout June, July, and August.1
Severe storms: In areas like Switzerland, violent storms and flooding were reported during the summer months.4
Agricultural impact: The unseasonable cold caused widespread crop failures and famines, leading to starvation in affected regions.12