A Blue Moon And Outrageous Heat Are On The Way To Montgomery County

Once in a blue moon? That’ll be Friday, the first in nearly three years.

A blue moon occurs when there are two full moons in the same month. Because a moon cycle lasts for about a month, the timing has to be just right to get two in the same month.

July 2 was a full moon. July 31 will be, too. Hence, blue moon 2015.

The last time this happened was August 2012, when there was a full moon on August 31 that year.

Meanwhile, the weather this week will be outstandingly hot. A hazardous weather warning has been issued for Montgomery County and much of southeastern Pennsylvania, per the National Weather Service.

Heat index values could reach 100 degrees on Wednesday afternoon, and extremely hot temperatures are expected to last from Tuesday through the blue moon event on Friday.

Thunderstorms and showers are possible Wednesday night and Thursday, and likely on Thursday night.

Here’s your full forecast:

Tuesday: Mostly sunny, with a high near 91. Calm wind.

Tuesday night: Mostly clear, with a low around 70. Light south wind.

Wednesday: Sunny, with a high near 92. Calm wind becoming southwest 5 to 7 mph in the afternoon.

Wednesday Night: A slight chance of showers after 2am. Mostly clear, with a low around 72. South wind 3 to 5 mph. Chance of precipitation is 20%.

Thursday: A slight chance of showers, then a chance of showers and thunderstorms after 11am. Mostly sunny, with a high near 92. Southwest wind 5 to 9 mph. Chance of precipitation is 40%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Thursday Night: Showers and thunderstorms likely between 8 pm and midnight, then a slight chance of showers. Mostly cloudy, with a low around 69. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Friday: Sunny, with a high near 92.

Friday Night: Mostly clear, with a low around 69.

The next blue moon will be an even rarer event.

Because of their timing coinciding with a leap year, both January and March of 2018 will have a blue moon. The last time that happened was 1999.

To answer a common question: no, the moon won’t actually be the color blue.

While there are some conditions that can cause the moon to appear a shade of blue—smoke, a concentration of certain particles—the name has nothing to do with the moon’s color.

It dates back to a 16th-century piece of literature using the word “belewe,” to betray, to refer to a moon that doesn’t properly mark the end of a farming season.

The “blue” caught on in the early 1900s and now generally refers to two full moons in the same month.