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Category Archives: Climate
Is there a windiest time of year in Madison?
With the pollen season peaking in southern Wisconsin one may wonder if there actually is a windiest time of year in Madison. Of course, a windy day can come along just about any time of year (the record gust of 83 mph in Madison occurred in June 1975) but the climatology suggests that March and April are the windiest months of the year with average wind speeds of 11.3 and 11.4 mph, respectively. November through February are not far behind logging a four-month average of 10.5 mph.
The fact that it’s windier during the cold season is not surprising as that time of year is characterized by the highest frequency of mid-latitude cyclone activity. Mid-latitude cyclones are large in scale, covering several states simultaneously, and are often associated with very large differences in sea-level pressure over small distances. It is these pressure differences that drive the wind. Continue reading
Category: Climate, Seasons, Severe Weather
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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
Should we stop climate research?
Scientific evidence for slow, ongoing, systematic warming of Earth’s atmosphere is unequivocal. This conclusion comes from evidence-based science and a physical understanding of that evidence. Regular scientific assessments of global and regional climate began in the 1970s. These assessments, along with a physical understanding of the atmosphere, show that the impact of human activities on this warming has evolved from theory to established fact. This is not a radical political statement; it is a firm conclusion based on the analysis of carefully considered observations.
Burning fossil fuels generates greenhouse gases, which are transparent to solar radiation but absorb large amounts of terrestrial infrared radiation that results in warming the atmosphere. The planet’s average surface temperature has risen about 2 degrees Fahrenheit since the late 1800s. Most of that warming has occurred in the past 40 years. Continue reading
How do we measure global cloud cover?
Because clouds are involved in the global water cycle as well as our planet’s energy gains and losses, they constitute an important component of our atmosphere, weather, and climate.
Determining global cloud cover requires observations that cover the entire planet. Observations from weather satellites provide a modern estimate of the global cloud cover. These satellites are operated by several countries and their data is shared through international agreements. Discrimination between clear and cloudy regions is a crucial first step in most applications of satellite data, such as estimating ocean temperature or assessing the health of land vegetation. Continue reading
Beyond the headlines, what else has been happening in the weather lately?
There has certainly been a lot of interesting and, in many cases, devastating weather around the country in the past couple of weeks. The heavy snow in parts of the country that don’t often see it along with the California wildfires have caught the attention of lots of us in the first days of the new year.
But in the background is a rather remarkable one-week stretch that occurred in the last week of December. Continue reading
