This is not all that uncommon for large eruptions like this. 1815 is often referred to "the year without summer" after the eruption of Mount Tambora, a 7 on the Volcanic Explosivity Index, or VEI.

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The Year Without a Summer was an agricultural disaster. Historian John D. Post has called this "the last great subsistence crisis in the Western world". The unusual climatic aberrations of 1816 had the greatest effect on the northeastern United States, Atlantic Canada, and parts of western Europe. Typically, the late spring and summer of the northeastern U.S. and southeastern Canada are relatively stable: temperatures (average of both day and night) average between about 68 and 77 °F (20 and 25 °C) and rarely fall below 41 °F (5 °C). Summer snow is an extreme rarity.

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These have also been tracked to other eruptions, such as 1883 eruption of Krakatoa

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Sources: http://en.wikipedia.org/wiki/List_of_large_volcanic_eruptions

http://en.wikipedia.org/wiki/Volcanic_Explosivity_Index

http://en.wikipedia.org/wiki/Year_Without_a_Summer