Spring is a season of renewal, growth and change. It comes after a long winter, and it's the season that brings the most beautiful blooms to the garden and yard. In the spring, flower bulbs planted in the fall explode into a riot of color. And the tulips, daffodils and other perennials grow larger than ever before. But sometimes a frost can rob the garden of its beauty and leave behind nothing but dead stems and leaves.

Frost is a period of sub-zero temperatures that damage plants by freezing and damaging tissues. It typically occurs in winter or early spring, but can occur at any time of year. The severity and impact of frost depends on local climate, soil conditions and plant types.

For many regions in Europe, frost events occurred earlier than normal during spring 2021 (Figure 1). This was primarily due to warmer-than-average temperatures across the UK and Ireland, northern France, southern Germany and Poland, although colder-than-normal conditions also affected much of central Europe.

Astronomical seasons are based on the Earth's changing position in relation to the Sun, and the resulting solar events of the equinoxes and solstices. Astronomical seasons start at the moment of the March equinox, end with the June solstice in the Northern Hemisphere, and start again at the September equinox in the Southern Hemisphere. Meteorological seasons, on the other hand, are based on the 12-month calendar and the annual temperature cycle. They are defined as beginning on the first of a month, so that spring starts on March 1, summer on June 1, autumn on September 1 and winter on December 1. The Old Farmer's Almanac uses the astronomical definition of the seasons.