Summer Heat

posted in: weather history, Weather ready nation | 11

Summer Heat Advisories

With the recent hot weather we had this past week I will post some information on different summer heat issues.

Heat Advisory

Issued within 12 hours of the onset of the following conditions: heat index of at least 105°F but less than 115°F for less than 3 hours per day, or nighttime lows above 80°F for 2 consecutive days.

Heat Index

The Heat Index (HI) or the “Apparent Temperature” is an accurate measure of how hot it really feels when the Relative Humidity (RH) is added to the actual air temperature.

What is the Heat Index?
The heat index is a measurement of how hot it really feels when the relative humidity is incorporated with the actual temperature. Heat indices were designed for use in the shade with light wind conditions. If in direct sunlight, the heat index can increase as much as 15°. With very hot and dry air, strong winds can also be extremely dangerous.

Heat Wave

A period of abnormally and uncomfortably hot and unusually humid weather. Typically a heat wave lasts two or more days.

What exactly is a heat wave?
A heat wave is a prolonged period of excessive heat and humidity. An Excessive Heat Warning is issued if the heat index equals or exceeds 105° for at least three consecutive hours. Heat Advisories are posted when the heat index is expected to exceed 100° for three consecutive hour and can be extended into the night if low temperatures are in the 70s or higher. Excessive Heat Warnings and Heat Advisories can be issued below criteria with additional guidance or a prolonged event is occurring or forecas

Excessive Heat

Excessive heat occurs from a combination of high temperatures (significantly above normal) and high humidities. At certain levels, the human body cannot maintain proper internal temperatures and may experience heat stroke. The “Heat Index” is a measure of the effect of the combined elements on the body.

Excessive Heat Outlook

This CPC product, a combination of temperature and humidity over a certain number of days, is designed to provide an indication of areas of the country where people and animals may need to take precautions against the heat during May to November.

Excessive Heat Warning

Issued within 12 hours of the onset of the following criteria: heat index of at least 105°F for more than 3 hours per day for 2 consecutive days, or heat index more than 115°F for any period of time.

Excessive Heat Watch

Issued by the National Weather Service when heat indices in excess of 105ºF (41ºC) during the day combined with nighttime low temperatures of 80ºF (27ºC) or higher are forecast to occur for two consecutive days

It is a judgment call as to what is “hot” but I will use a high of 88 or better. On average Grand Rapids has a all time average of around 20 days a year of 88 or better with a range of 45 in 1921 to a low of just 2 in 2000. Last year there were 18 such days. For a comparison in the winter season on average there are on average 54 days of highs of 32 or lower with a range of 84 in 1978 to a low of 20 in 1931.

Here is how Weatherspark describes the summer season in Grand Rapids.

Summer Weather in Grand Rapids Michigan, United States

“Daily high temperatures are around 79°F, rarely falling below 64°F or exceeding 90°F. The highest daily average high temperature is 83°F on July 19.

Daily low temperatures increase by 4°F, from 54°F to 59°F, rarely falling below 44°F or exceeding 72°F. The highest daily average low temperature is 63°F on July 20.

For reference, on July 19, the hottest day of the year, temperatures in Grand Rapids typically range from 63°F to 83°F, while on January 29, Summer Weather in Grand Rapids Michigan, United States

Daily high temperatures are around 79°F, rarely falling below 64°F or exceeding 90°F. The highest daily average high temperature is 83°F on July 19.

Daily low temperatures increase by 4°F, from 54°F to 59°F, rarely falling below 44°F or exceeding 72°F. The highest daily average low temperature is 63°F on July 20.

For reference, on July 19, the hottest day of the year, temperatures in Grand Rapids typically range from 63°F to 83°F, while on January 29, the coldest day of the year, they range from 18°F to 30°F.”

Slim

 

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Kyle (Portland, Ionia County)
Kyle (Portland, Ionia County)

I believe the last derecho to impact Grand Rapids was 2019. I was storm chasing that night it was a late night event. There was a watch up for Big Rapids area and north so I was in Reed City waiting on the line. Well the more it moved east it started to dive south so I headed south. I stayed right on the leading edge of the gust front all the way down Rockford before the line caught up to me. The power at the meijer along the Highway was flashing on and off. The line kept going down… Read more »

Kyle (Portland, Ionia County)
Kyle (Portland, Ionia County)

On this date in 2010 we had a derecho moving across the Midwest. The first wind reports began in Nebraska then became more widespread across Iowa, Illinois, Southern Wisconsin and Then right here into Southern Lower MI (generally I-96 and southward). There was a wind gust close to 80mph near Three Rivers. DCAPE values were 1,200-1,300 as this line moved into lower Michigan. Highest CAPE was south of 96 right in line with the most intense winds and damage.

INDY
INDY

Summer heat …52* degrees out in my hood feels fresh ….INDY

Rocky (Rockford)
Rocky (Rockford)

Yes, great cool weather weekend! Bring it!

Rocky (Rockford)
Rocky (Rockford)

Lows in the 40’s again tonight! Incredible cold!

Mark (East Lansing)
Mark (East Lansing)

Again? Where? 50s here.

Rocky (Rockford)
Rocky (Rockford)

Tonight in GR baby and last night just NE of GR! Incredible cold!

Rocky (Rockford)
Rocky (Rockford)

Very cold temps last night and a low high temp today! Wow and if it would only last!