The Amazing 5th Day Climatological Significance

By: Mark Bloomer, Meteorologist

Maine seasons are very pronounced with strong contrasts between our cold and snowy winters and our warm and colorful summers. Our transitional seasons of spring and fall bring dramatic changes from muddy to green in the spring and from golden to grey in the fall. Each month has specific dates that mark significant astronomical or climatological changes in the season.

We are all familiar with the solstices and the equinoxes. The longest day of the year, around June 21st, has almost twice the daylight length than the shortest day of the year, December 21st. The times of year when the length of the day equals the length of the night include the spring and fall equinoxes, around March 21st and September 21st. But there are many other significant dates during the year that have climatological significance. In fact, the 5th day of each and every month happens to have special climatological significance.

January 5th begins the coldest one month period of the year. During this time, both high and low temperatures average the lowest that they do all year.

February 5th is the first day of solar spring. Although winter may still be in full force at this time, it may be reassuring to know that February 5th is the end of the darkest quarter of the year, the end of the coldest one month period of the year, and the beginning of the of the three month period that brings the most rapid increase in day length.

March 5th is the beginning of climatological spring. It marks the end of the coldest quarter of the year, and the beginning of the three month period of greatest temperature rise.

April 5th is the beginning of the one month period that brings the most rapid temperature increase in the northern hemisphere. Averages rise around 15 degrees in Maine during this one month period ending May 5th.

May 5th is the beginning of solar summer, which is the brightest third of the year. The middle of this period is June 21st which is the summer solstice, the longest day of the year.

June 5th is the beginning of meteorological summer, the warmest three months of the year.

July 5th begins the hottest month of the year when averages are at their highest.

August 5th is still in the deep of the summer, but is a significant turning point into early autumn. August 5th is the end of solar summer and the beginning of solar fall, the quarter of the year that brings the most rapid decrease in day length. August 5th also ends the hottest monthly period of the year.

September 5th is the first day of climatological fall, the one month period that brings the most rapid decrease in average temperatures.

October 5th begins the one month period of most rapid cooling. Averages drop around 15 degrees from October 5th to November 5th.

November 5th is the beginning of solar winter. This is the start of the three month period when days are shortest and nights are longest.

December 5th is the beginning of meteorological winter. It is the start of the coldest three month period, and the start of the one month period of shortest days and longest nights.

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