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Category Archives: Climate
What is a water year and what is it used for?
A water year is used in hydrology to describe the 12-month period for which precipitation totals of an area are determined.
The U.S. Geological Survey, or USGS, operates a nationwide system of instruments to monitor discharge in rivers and issues comprehensive reports on the use of water resources. The USGS defines a water year as the 12-month period from Oct. 1 through Sept. 30 of the following year. This definition standardizes the reporting of water statistics in their publications. The water year is designated by the calendar year in which it ends, so on Oct. 1 we entered water year 2027. Continue reading
Why is the reference, or normal, climate period a 30-year average?
Climate normals are 30-year averages for various climate observations such as temperature, precipitation and snowfall. A 30-year period smooths out weather variability while getting a good representation of our current climate. The current 30-year normal covers the period 1991-2020. This averaging provides a baseline for comparisons and assessing whether a particular day or month is warmer or cooler than normal, or if it is wetter or drier than normal.
The World Meteorological Organization (WMO) recommends 30 years as the reference for current average conditions, and member nations follow that recommendation. For the United States, NOAA’s National Center for Environmental Information (NCEI) is the official source of the country’s climate normals. The computation is nontrivial and more complicated than one might initially anticipate. Climate scientists employ complex statistical calculations to ensure the observations accurately represent the full 30-year climate period. The determination of normal must account for the occasional missing data, change in station location and instrument upgrades. Continue reading
How did our summer look climatologically?
Meteorological summer is defined as the weather from June 1 through Aug. 31. The reference, or normal, climate period is the 30-year period of 1991-2020. The State Climatology Office recently completed its analysis of our 2026 summer conditions and created a comparison with previous summers.
The statewide average temperature during the summer of 2026 was 68.5 Fahrenheit, which is 1.3 degrees above normal. This was the seventh consecutive summer during which Wisconsin experienced a warmer-than-average temperature. All three summer months were above their normal monthly temperature. The largest departures of three to four degrees were scattered throughout northern Wisconsin. Continue reading
Is wildfire season getting longer?
Wildfires are an important part of many ecosystems and an essential part of forest and rangeland health.
Fires require fuel to burn, heat to ignite and oxygen to burn. Wildfire season is defined as the time of year when wildfires are most likely to ignite and spread. A combination of high temperatures, low humidity, lack of precipitation days and high winds make wildfires more likely to spread and lengthen fire seasons. Continue reading
Was this spring milder than normal?
With only a few exceptions, it seems as if this year’s run-up to summer, which arrived at 3:24 a.m. Sunday, June 21, was relatively mild. By that we mean very few really oppressively hot and humid days.
Naturally, we wondered if this were actually a true impression and also how this year’s spring stacked up against others that have visited Madison over the years. One way (but not the only way) to make such an assessment is to consider how many days in the interval from April 1 to June 21 have had a daily high temperature greater than or equal to 80 degrees Fahrenheit. Continue reading
