Summer's here! Here's the weather we're expecting, and why

Depending on which summer you observe (meteorological, astronomical, or holiday), summer has either already begun or it starts next week. Meteorological summer started on June 1st; astronomical summer begins with the Summer Solstice, which this year is on June 21st; Memorial Day kicks off the summer season for beach towns in the Tri-State. This is the time of year when we see the most thunderstorms and everything that comes with them, like lightning, hail, and damaging winds. Here's a breakdown of common summer weather phenomena in the Tri-State, including thunderstorms, and why they happen more often this time of year.

Seabreezes
Seabreezes are great for cooling us off on hot days at the beach. They're most common on sunny days early in the summer, when ocean temperatures are in the 50s and 60s. This is because seabreezes are dependent on a temperature difference between ocean and land. The seabreeze often doesn't "kick in" until the afternoon for this same reason.
As land near the ocean heats up after sunrise, the air rises. Remember that warm air is less dense than cold air. So as the warming air rises over land. cooler denser air above the ocean rushes in to replace it. And, since that air is denser than the rising warm air, it stays close to the surface (or, in this case, the sand). This is what we feel as a seabreeze. 

Along with a seabreeze, you'll often see puffy clouds form near the water's edge 

when ocean temperatures are cooler than they are inland. (photo taken by me)

Rainbows
Of course, rainbows are not exclusive to the summer months, but they're a lot more common in the Tri-State this time of year because heat and humidity is higher in the summer. This combo is conducive to the formation of convective showers and thunderstorms in the late afternoon and early evening, when the sun angle is best for rainbows. 
Rainbows are optical illusions, created by sunlight passing through water droplets, which act as tiny prisms to separate the sun's rays into all the colors of the rainbow. The rainbow is then projected in the opposite direction of the setting sun, and it's much easier for us to see it when it's cloudy in that direction. This allows the clouds to act as a white or gray projector screen. 
Since most thunderstorms in the Tri-State move from west to east, and the sun sets in the west, your best bet to see a rainbow is to look eastward after a rain shower or storm. That's what I did when I captured the beautiful image below: 

Did you know that a double rainbow is just a reflection of the main rainbow?
Notice that the top rainbow's colors are in reverse order of the bottom one.

(photo taken by me)

Rainbows can happen early in the day, of course, but we don't see them as often because all the elements described above don't come together. It's pretty uncommon in the Northeast for a rain shower to move from east to west as the sun is rising. And we can forget about a mid-day rainbow; with the sun's rays directly overhead, there's nowhere for the prism's image to go. 
So, why don't we see more rainbows in the winter, when the sun is low in the sky for a longer percentage of the day? The main reasons are:

- Snowflakes don't refract the sun's rays like a prism. Instead, snowflakes appear white because they scatter all the wavelength colors that come from the sun. 

- When it rains in the winter, it usually comes from stratus clouds, which blanket the whole sky. The pop-up convective clouds we see more often in the summer allow the sun to poke through. 

Severe thunderstorms
As mentioned above, convective clouds are more common in the summer than in the winter. That's due to an increase in lapse rates in the Northern Hemisphere summer. In the winter, the temperature difference from the surface to a few thousand feet aloft is smaller, on average, than it is in the summer. When the temperature drops quickly with height, it causes instability. Remember from the seabreeze example that colder air sinks and warm air rises? Higher lapse rates cause this type of vertical instability more frequently in the summer. And when there's enough humidity present, you can get towering cumulonimbus clouds to form, like the one in the photo below. 

Severe thunderstorms often have an anvil shape, like this one. 

This cloud can only form if it's much warmer at the surface than it is aloft. 

Photo taken by 2022 AMS Weather Band Photo Contest runner-up, Jim Conley.

As the word "instability" may indicate, this process and the clouds that result are more conducive to severe thunderstorms. When the clouds grow tall enough, they can displace cold air aloft and cause it to sink rapidly to the ground. This is called a downburst. Hail also forms in clouds like the one above; as raindrops get tossed upward and freeze, they form hailstones, which are eventually carried back to the surface by gravity or surface-bound winds called downdrafts. The rotating columns of air that cause tornadoes are more complicated, but are also a result of an unstable atmosphere. (You can find an awesome webinar about tornadogenesis here.)  

Heat lightning
Before we go any further, let's start with the fact that heat does NOT create lightning, so "heat lightning" is not an actual thing! But I think this misleading moniker comes from its frequent summer occurrence. 

Intra-cloud lightning is sometimes seen, but not heard as thunder.
Photo by 2022 AMS Weather Band Photo Contest runner-up, Brad Nelson

The phenomenon we've come to know as heat lightning is really just lightning that is so far away that we can't hear the thunder. It's more common in the summer, not just because we get more storms at this time of year, but also because it's when storm clouds tend to grow taller. Some of that lightning is happening miles above the surface, inside of the cloud and never reaching the ground. Since this intra-cloud lightning is happening so high up, there's an increased chance it'll be too far away for us to hear. And, water in the cloud muffles the sound of thunder more than air near the surface. The old rule "When Thunder Roars, Head Indoors" applies here too. If you see lightning strikes inside a cloud but never hear thunder, it's likely that the storm is farther away than it looks.