CIMSS

The forecast for D-Day turned the tide of history:

How important was the weather forecast on D-Day? D-Day was the name given to the June 6, 1944, invasion of the beaches at Normandy in northern France by troops of the Allied Forces during World War II. The goal was to cross the narrow, often stormy, English Channel into Nazi-occupied France.The successful D-Day invasion required a combination of e...

What are the dangers associated with fire weather? Ask the Weather Guys!

What is fire weather? Wildfires need three essential elements: heat, oxygen and dry fuel. Fire weather refers to a mix of meteorological conditions that make it easy for wildfires to ignite and spread quickly. The main weather factors are low humidity, strong winds, warm temperatures and atmospheric instability.When humi...

Who or what activates the warning sirens in your area? Ask the Weather Guys!

Who or what triggers the decision to sound a tornado siren? The National Weather Service is responsible for issuing forecasts, watches and warnings for a variety of weather and water hazards. A

GOES-16 is out of storage for testing for about 2 weeks. Here is a full disk image with the CIMSS Natural Color enhancement today (5/15/2026) at 19:00 UTC, which is local noon for the satellite. It's a slightly different view from what we're used to from GOES-East (75W) or GOES-West (137W) since it is centered at 105W.

Why are robins arriving so early? Ask the Weather Guys!

Is global warming impacting bird migration? Global warming refers to the rise in global temperatures due to the increasing concentrations of greenhouse gases in the atmosphere. One impact is that northern latitudes are experiencing warmer mean annual temperatures and experiencing earlier springs, milder winters and delayed falls.Bird migratio...

How is a tornado rated? Ask the Weather Guys!

What is the tornado scale? A tornado is a powerful column of winds that rotate around a center of low pressure. The winds inside a tornado spiral inward and upward, often exceeding speeds of 300 mph. We classify the strength of a tornado after trained observers assess the damage it did to the area.All tornadoes are assigned a...

What does it mean when you see green clouds during a storm? Ask the Weather Guys!

Why do clouds turn green during some storms? The visible light spectrum covers colors from violet to red. Each color corresponds to a different wavelength, with green sitting roughly in the middle. Blue and violet have shorter wavelengths. Light rays change direction when they hit particles — a process known as scattering. The sky looks blue...

Are cartoonists right in showing raindrops shaped like tears? Ask the Weather Guys!

What is the shape of raindrops? While cartoonists typically draw raindrops like a teardrop or a pear shape, raindrops are not shaped like that.They are drawn as teardrops to give the image of falling through the atmosphere, which they do. But as they fall, raindrops are flattened and shaped like a hamburger bun by the drag forces....

What are iceballs? Linda Deith asked the Weather Guys:

What are ice balls and how do they form? If you were lucky enough to be walking along Lake Mendota shoreline at Shorewood Hills and Frautschi Point on March 16, 2026, you might have seen ice balls, or ice eggs, floating in the water. This was a rare occurrence of naturally formed balls of ice that form in cold water.While they look a littl...