Oh, there's been plenty of 3 year periods of huge disasters. 1996-1999 is a good period to look at:
Sept. 14ñ18, Bahamas to New England: ìFloydî and associated flooding caused at least 57 deaths including one in the Bahamas. Hardest-hit N.C. suffered
35 ìFloydî related deaths. Deadliest U.S. hurricane since ìAgnesî in 1972. Damage estimated at $4.5 billion (actual cost).
Jan. 6ñ8, eastern U.S.: heavy snow paralyzed the Appalachians, the mid-Atlantic, and the Northeast. 187 were killed in the blizzard and in the floods
that resulted after a sudden warm-up. Damages reached $3 billion.
May 27, central Tex.: multiple tornadoes, including one particularly strong twister that devastated the town of Jarrell, caused 29 deaths and an
estimated $20 million in damage.
Jan. 17ñ22, Tenn. and Ark.: a series of tornadoes left 17 dead. Damages were estimated at $1.3 billion.
May 3, Okla. and Kans.: unusually large twister, thought to have been a mile wide at times, killed 41 people and injured at least 748 others in Okla.
A separate tornado killed another 5 and injured about 150 in Kans. Damages totaled at least $1 billion.
TERRORIST ATTACKS ON US CITIZENS:
Aug. 7, Nairobi, Kenya, and Dar es Salaam, Tanzania: truck bombs exploded almost simultaneously near two U.S. embassies, killing 224 (213 in Kenya and
11 in Tanzania) and injuring about 4,500. Four men, two of whom had received training at al-Qaeda camps inside Afghanistan, were convicted of the
killings in May 2001 and later sentenced to life in prison. A federal grand jury had indicted 22 men in connection with the attacks, including Saudi
dissident Osama bin Laden, who remained at large.
May 11, Everglades, Fla.: ValuJet DC-9 went down in swamp, killing 110. Cargo fire caused by oxygen generators missing safety caps.
July 17, off coast of Long Island, N.Y.: TWA Boeing 747-100 bound for Paris from N.Y. exploded over waters of eastern L.I. and crashed into Atlantic
Ocean, killing all 230 aboard.
Summer, southern U.S.: severe heat and drought spread across Tex. and Okla., all the way to North and South Carolina. At least 200 were left dead and
$6ñ9 billion of damage was estimated.
Summer, eastern U.S.: rainfall shortages resulted in worst drought on record for Md., Del., N.J., and R.I. The state of W.Va. was declared a disaster
area. 3.81 million acres were consumed by fire as of mid-Aug. Crops were severely damaged in many states, putting losses in the mid-Atlantic region at
at least $800 million. Record heat throughout the country resulted in 282 deaths nationwide.
You can research it for yourself here:
There's some good candidates for 'high disaster triples' in the 1980's as well.