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Category Archives: Seasons
When will we have our last spring frost?
The latest frost in spring is important to gardeners as we seek to protect our garden plants from freezing temperatures. For Madison, based on temperature observations between 1940 and 2024, the latest frost occurred on 10 June 1972 and the earliest final frost occurred on 7 April 1955. The last frost date varies from year to year as it is strongly dependent on current weather conditions. To best estimate the last frost is to use statistics over a given time period. The median date for the last frost in Madison is May 5. Giving the median date of last frost means that there is still a 50% chance that a frost will occur after this date.
An analysis of Madison’s last frost date from 1940 – 2024 shows a trend consistent with the scientific expectations of global warming, that the last frost date now occurs earlier in the spring. Our nighttime minimum temperatures have been getting warmer and that too is consistent with the last frost date moving earlier. Continue reading
Why does the severe weather threat increase as spring and summer approach?
As the threat of winter snows recedes across the country, it is replaced by the threat of severe weather (i.e. thunderstorms with hail, damaging winds and tornadoes).
The severe weather season, though broadly spanning March through August across the United States, is actually quite regional. It begins in March in the southern states, moves to the southern Plains during April and May, and then further north toward the Great Lakes states during the summer. Continue reading
Category: Meteorology, Seasons, Severe Weather
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Was 2024 an interesting weather year for Wisconsin?
Yes, 2024 was a very interesting year. The statewide average temperature was 31.4 degrees Fahrenheit, which is 12.2 degrees warmer than the 1991-2020 normal. December 2023 to February 2024 was our warmest winter since record-keeping began in 1895. The statewide average temperature for the winter was 28.3 degrees, surpassing the previous record by 2 degrees.
Wisconsin’s average temperature during November 2024 was 38.7 degrees, which is 7.1 degrees above the November average temperature. Seventy out of Wisconsin’s 72 counties recorded a November 2024 average temperature much above average. Overall, 2024 is on track to be Wisconsin’s warmest year on record. Continue reading
What is the difference between sleet and freezing rain?
Rain, snow, freezing rain, and sleet all generate hazardous traffic conditions. Freezing rain, and the less intense freezing drizzle, can create the very treacherous road condition referred to as “black ice.” A freezing fog may similarly coat objects in ice while also reducing visibility. Black ice is so named because the affected roadway appears dark, just like wet pavement. Black ice creates nearly zero friction conditions with vehicle tires so that correcting a skid in such conditions can be nearly impossible. Continue reading
Category: Meteorology, Seasons
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Does the warmest autumn on record mean anything about the coming winter?
In the past several years we have occasionally mentioned our tracking of the areal extent of air colder than minus 5 degrees centigrade at about 1 mile above the surface of the Earth. This measurement has proven to be a very valuable addition to the collection of metrics of global warming. We have particularly commented on the wintertime (December, January and February) average of this extent measured over the entire Northern Hemisphere, noting that since 1948 the wintertime average extent has systematically decreased.
We have also been tracking this variable throughout the autumn over all these years and can report that this fall (Sept. through Nov. 30) recorded the smallest average areal extent of this cold air since at least 1948. That means we have just experienced the warmest Northern Hemisphere autumn in at least the past 77 years. Continue reading
