Spring is usually the height of severe weather season in the United States. This year, however, it has been slow going – at least so far.

According to NOAA’s Storm Prediction Center, there have only been 20 tornadoes rated EF-1 or higher to date in 2014. On average, we usually see 157 storms by this point in the season. Of the twisters that did form, none were rated EF-3 or stronger. That is fairly weak by tornado standards, which are measured from EF-0 to EF-5 on the Enhanced Fujita (EF) scale.

With colder than average temperatures dominating most of the country recently, storm development – which needs warm moist air and explosive convection – has been limited. That said, a slow start does not necessarily mean a slow season. It only takes one strong storm to devastate an area. Last year, for example, was a below average season, but it still produced an EF-5 that leveled Moore, OK.

May is typically the most active month of the year for tornadoes in the US.

Data Source: NOAA