The U.S. appears to be locked in a tornado drought, as meteorologists have recorded only about two-dozen twisters so far this year during a period when 100 or more are typical.

There also have been no reports of tornadoes during the month of March—a sometimes violent period for severe weather. The last time there were no tornadoes in March was 1969.

Forecasters at NOAA’s Storm Prediction Center have issued only four tornado watches and no severe thunderstorm watches—less than 10 percent of the average 52 tornado watches issued by mid-March.

Warning coordination meteorologist Greg Carbin said there isn’t one answer to explain the sluggish start but noted a persistent weather pattern of cold, stable air prevents a tornado’s ingredients from coming together.