ASK TOM WHY: Do you crack the windows in your house during a tornado?

Dear Tom,

I have heard you should crack the windows in your house during a tornado. Please give me your thoughts.

Rich Middleton, Rockford

Dear Rich,

Do NOT do that. It’s a notion conclusively laid to rest by research conducted in 1977 by an engineering team at Texas Tech’s Institute for Disaster Research and further discredited by all that’s now known about how tornadoes work. Opening windows in or near tornadoes is a useless exercise and a waste of precious time that ought to be used in getting yourself and those you are responsible for to a safer location. In fact, it may actually contribute to damage to the house.The pressure drop in the strongest tornadoes is about 10 percent, and that pressure decline can be vented by the normal openings in a house in just three seconds, even with the windows closed.

ASK TOM WHY: How many past Good Fridays have experienced rain or snow?

Dear Tom,

How many past Good Fridays have experienced rain or snow?

— Michael K. Garrison,

Dear Michael,

Good Fridays do show a bias toward precipitation. With the help of Chicago weather historian and climatologist Frank Wachowski, we checked the weather on 143 Good Fridays dating to 1871. Measurable precipitation has occurred in 73 years, or 51 percent of the days, at a time of the year when the daily climatological expectation for precipitation is about 40 percent. When traces of rain and snow are added to the mix, the percentage jumps to 64 percent as compared with an expectation of 56 percent. The last rain to fall on Good Friday was April 22, 2011, when more than half an inch soaked the city.

ASK TOM: Bright green streak falling star.

Dear Tom,

In late March I saw a bright green streak, a falling star. What accounts for that color? Air pollution?

— Frank Dezio

Dear Frank,

Meteoroids, orbiting the sun in huge numbers, are believed to be debris left over from the formation of the solar system.

They are occasionally captured by the Earth’s gravitational pull and, plunging at speeds up to150,000 mph, glow to incandescence because of friction with the atmosphere.

A brief streak of light, usually whitish, is the familiar result.

But astronomer Dan Joyce of Triton College tells us that a distinct green color is not rare.

The color of the streak has nothing to do with the atmosphere, he says.

The composition of the meteoroid is probably a reason for the color, and he suspects it is likely chromium.

ASK TOM: How are very abnormal temperatures figured into Chicago’s “normal” temps?

Dear Tom,

Over what period of time have Chicago’s daily normals been calculated? How are the very abnormal temperatures like our very cold winter figured into the normals?

— Tig White, Chicago


Dear Tig,

The National Weather Service’s National Climatic Data Center in Asheville, N.C., calculates the official normal daily high and low temperatures used in the U.S. By international agreement, normals are simple arithmetic averages of weather variables over 30 years, generally three consecutive decades, and they are recalculated each decade. Normals now in use cover the period 1981-2010.

Unusual temperatures are factored into the calculations just like any other readings.

Don’t overinterpret normal values. They don’t even represent what should happen; they are merely averages.

ASK TOM: What is an “embedded thunderstorm”?

Dear Tom,

What is an “embedded thunderstorm”?

– June Wheeler,  Madison, Wis.

Dear June,

Webster’s New World Dictionary defines “embed” this way: “To set or fix firmly in a surrounding mass.” The precipitation that falls with major storm systems often extends across areas as large as several Midwestern states. Meteorologists refer to these as “synoptic scale” events. This kind of precipitation distribution differs from the relatively narrow bands or isolated clusters of showers and thunderstorms that usually occur in the warm season.

When In a situation in which a large precipitation area includes scattered thunderstorms, those storms are said to be “embedded” within the larger precipitation area. A forecast of rain and embedded thunderstorms suggests an extended period of rain that might occasionally include a thunderstorm.

ASK TOM WHY: How windy was it for the May 17, 1979 Cubs game at Wrigley Field?

Dear Tom,

How windy was it for the May 17, 1979 Cubs game at Wrigley Field when the Phillies beat the Cubs 23-22?

Allen Moody
Island Lake

Dear Allen,

There have been windier days at Wrigley Field, but the wind was definitely blowing out on the afternoon of May 17, 1979. According to Chicago weather historian Frank Wachowski, south winds were blowing straight out to left field at 20 mph with gusts in excess of 30 mph during the game. There were 11 home runs hit that day, including three by Cubs’ slugger Dave Kingman and two by Mike Schmidt of the Phillies. After one inning the Phillies led 7-6 and the Cubs overcame as 12-run deficit to tie the game in the 8th, only to lose it in the 10th on Schmidt’s second homer,

ASK TOM: Advice for those who fear thunder

Dear Tom,

My 5-year-old, Jenny, is mildly afraid of thunder and lightning. Do you have any advice for her?

— Jim Sumner, Schaumburg

Dear Jenny,

You’re not alone in being frightened of thunderstorms. Many grown-ups find them to be scary. But because they are older and have witnessed many storms, they know how to stay safe. Thunderstorms have always been around, and they aren’t all bad. They lower temperatures on very hot days, and they bring needed water to our ponds and lakes and our thirsty lawns and farm plants. Thunderstorm rain cleans pollution out of the air. Lightning even makes fertilizer from nitrogen in the air, and that fertilizer falls with rain. It is important to know that most storms are not damaging, and you will be safe if you go indoors. Warnings are issued for dangerous storms.

ASK TOM WHY: Has a record high and low temperature ever been set on the same day one year apart?

Dear Tom,

Has a record high and low temperature ever been set on the same day one year apart?

Steven Pacific

Dear Steven,
It has occurred several times, but none more dramatic than the periods leading up to Christmas in 1982 and 1983. Driven by a strong El Nino, Chicago established balmy record highs of 62 degrees on December 23 and 64 degrees on Christmas Day in 1982. The next year with a persistent Siberian Express in control, record lows of minus 21 and minus 17 were logged respectively on the same dates. Other occurrences of year-apart record highs and lows- April 21 1985- 88 degrees -1986 27 degrees, May 11, 1982-89 degrees 1981-33 degrees, July 28, 1983-100 degrees, 1984-51 degrees, and October 21, 1953-87 degrees, 1952-26 degrees.

ASK TOM: Guidelines for suspending outdoor activities when lightning and t-storms threaten

Dear Tom,

What are the guidelines for suspending outdoor activities like baseball when lightning and thunderstorms threaten?

— Andrew Reinhardt


Dear Andrew,

All safety experts say outdoor activities should cease immediately when thunder is heard. Thunder is a byproduct of lightning, so if thunder is heard, lighting is present. This might not be apparent in daytime thunderstorms, when lightning flashes compete with daylight and are hard to see. The National Collegiate Athletic Association handbook of lightning safety says thunder should prompt an evacuation of the field and that the refuge of a safe shelter should be sought. Furthermore, the handbook recommends that outdoor activities not resume until 30 minutes after the last rumble of thunder.

ASK TOM: Chicago area’s April 1961 snowstorm

Dear Tom,

Your column about the April 2-3, 1975 snowstorm reminded me about an April 16, 1961 snowstorm when my fiance and I were stranded at my parent’s Chicago Heights home after our engagement party. Details?

— Bonnie Zarch, Skokie

Dear Bonnie,

The Chicago area recorded its largest latest-in-the-season snowstorm when 6.8 inches fell April 15-17, 1961. The bulk of the snow came down on April 16, when the city’s official site at Midway Airport measured 5.4 inches. The heavy, wet snow, piled into 5-to-10-foot-high drifts by winds gusting to 50 mph, shut down many area roads. The snow was heaviest south and east of Chicago with 5-to-9-inch totals common between Chicago and Indianapolis. But temperatures quickly rebounded into the 60s, melting the snow within a day or two.