GWC Monthly Summary – December 2024
Review – December 2024 – Snow Squall and Rainy End to Year
The month of December 2024 began dry with no measurable rainfall for 9 of the first 14 days. However, a snow squall developed on December 5th to provide the month’s first weather highlight at Greg’s Weather Center. The squall sparked a much wetter end to 2024. The year concluded with measurable precipitation in 15 of the last 17 days including snow on Christmas Eve and over a third of the month’s rainfall over the last five days of 2024.
View Local Climatological Data – Greg’s Weather Center – December 2024
Rainfall – December 2024
Nearly four inches of rain fell during the last month of 2024. After the drought that dominated much of the late summer and fall, there was a total of 6.67 inches of rainfall over the last 49 days of the year.
There were a total of 20 days with measurable precipitation during December 2024. The maximum rainfall rate for the month was 2.39 inches per hour which occurred on New Year’s Eve at 9:59 PM.
The peak rainfall capped off five consecutive days with measurable precipitation. The 24-hour period with the most rainfall in December 2024 occurred on the 10th and 11th.
| Date | Total Rainfall |
| December 27-31, 2024 | 1.37 inches |
| December 9-11, 2024 | 1.14 inches |
| December 15-17, 2024 | 0.75 inches |
| December 18-19, 2024 | 0.24 inches |
| December 4-5, 2024 | 0.12 inches |
| December 20-21, 2024 | 0.10 inches |
| December 24-26, 2024 | 0.09 inches |
Table 1: Rainfall at Greg’s Weather Center – December 2024
Wind – December 2024
Not only did this stormy end of 2024 bring more rainfall, but also an increase in winds. There were a dozen days with double-digit wind gusts at GWC in December 2024.
This included three straight days with double-digit wind gusts to end the year. The peak wind gust of 15 miles per hour occurred on December 12th.
This followed a gust of 13 miles per hour on December 11th. Both correlated with the minimum pressure of the month on December 11th.
The dominant wind direction during the month was from the Northwest, which helped usher in colder temperatures.
Temperature – December 2024
The last month of 2024 consisted of a vast range in temperature. The diurnal temperature range for the month was 56 degrees.
The volatility in temperature was especially prevalent over the last 9 days of the year. On the morning of December 23rd, the low was 8 degrees. From that point until the afternoon of December 29th, the thermometer rose 55 degrees to a high of 63 that day.
The thermometer climbed at a rate of over 9 degrees per day over the six days. There were 24 days where the low fell below freezing while another three had a high below 32 degrees as well. There were 17 days where the high temperature was at least 40 degrees including nine above 50 degrees.
The average high for the month was 42 degrees while the average low was 26. The average temperature for December 2024 was 35 degrees. Looking at the diurnal temperature range, the average for the month was 16 degrees.
Pressure – December 2024
The average barometric pressure for the month was 30.14 inches of Hg or 1021 millibars at GWC. The lowest pressure was 29.36 inches or 994 millibars on December 11th while the highest was 30.93 inches or 1047 millibars on December 14th. It was a classic case of a strong high following a strong low. Over the three days between the 11th and the 14th, the pressure rose 1.57 inches or 52.3 millibars. This was record high pressure.
According to the National Weather Service Office in Mount Holly, the barometric pressure at Philadelphia International Airport reached 1048.3 millibars or 30.96 inches at 10:00 AM on December 14th. It was less than a millibar short of the record for December set in 1949. It was the highest pressure recorded there since the all-time mark of 1053.2 millibars or 31.10 inches set on February 13, 1981.
There were several storms during the month including the aforementioned snow squall on the 5th and Christmas Eve snow. There was the strongest storm of the month on December 10-11 with the heaviest rainfall of this final month of 2024. Then, there was the stormy period that concluded the year with 1.37 inches of rain from December 27-31.
