June 21st is the day we celebrate the summer solstice! The time of the year when the Sun reaches its highest position in the sky. The longest day of the entire year. This day the sun, Sol, shines the longest and is at the height of its life-giving power. And, of course, the day we get to admire and enjoy the sunshine a little longer than usual.
Traditionally, in the northern hemisphere, It is the time of the first harvest. Pagans, Wiccans, and modern druids celebrate the day with rituals and festivals such as Yoga during the sunset or sunrise, Midsummer bonfire, and Perfect Alignment at the Stonehedge. Summer is a celebration of fire and power, the power that makes bountiful and nurtures tiny seeds. The immense power that the sun brings awakening, and symbolize spiritual enlightenment. 

In Pagan lore, the midsummer is the Sabbath of Litha and it is primarily celebrated by Wiccans. Traditionally the festival is celebrated for the entire day. It is the time where the god and goddess are married and the goddess is pregnant. In Litha, the god and goddess are considered to be at the most abundant and powerful round this time. Thus, passing on the energy and power to the land. Flowers are in full bloom, trees are the greenest they will be, crops are abundant and bountiful.
It is also the day when the season transitions from longer days and shorter nights to shorter days and longer nights.
Litha represents a symbolic yearly battle between the oak king and the holly king which is won by the latter and brings an end to the dark half of the year.
Aside from celebrating the sun, earth, prosperity, and joy, it is also about welcoming the sun's most potent energy, celebrating the long sunny days ahead as well as a preparation for shorter days and longer nights.

Traditions

Wear the colors of Litha.

One of the most simple things you can do during the Sabbath of Litha is to wear the colors that represent the Sabbath. It could be your clothes, accessories, makeup, or all of it together. If you feel like going all out then, by all means, do it. If you chose to be lowkey about it, that's okay too.

Read the correspondences below for the colors

The Midsummer Bonfire.

During midsummer eve, people would start setting the watch by building a big bonfire to ward off and keep evil spirits out of the town. People would dance around the fire to celebrate and jump over it for good luck. It is also recommended to carry a gemstone and whisper your intentions or requests as you circle the bonfire. After three laps around the fire, throw the stone into the flames. Usually, the ashes of the bonfire will then be sowed into your garden or crops to have a bountiful season.

Sunrise or sunset watching and yoga.

You can either admire and soak in the power of the sun through your window bay, on your porch, out in the field, or, if you are lucky enough to travel, at Stonehedge where most people gather for the summer solstice by walking among the stones. It is also great to soak in the meaning full day of transition and change by doing yoga. Performing sun salutations for the sunrise and sunset can be so powerful spiritual-wise.

Litha Altar Setting Ideas.

The Litha altar is most of the time vibrant and colorful. Since Litha is more on the solar festival, add lit candles in Litha colors. Don't forget to charge your crystals under the sunlight and place them on your altar. (Carefully) Burning oak wood and oak leaves are great to symbolize the transition of the season. 

Correspondences:

Colors of Litha

The main colors of Litha are blue, green, and gold which symbolizes fertility, prosperity, bountiful, and the sun. In addition to that are red, yellow, and orange to channel solar energy.

Crystals

Stones like jade, emerald, tiger's eye, topaz, amber, onyx are perfect to use to channel the energy during Litha. Remember, Litha is the perfect time to charge your crystals as the energy is immense. Although, careful with crystals that are sensitive to the sun.

Herbs

There are tons of herbs you can use during Litha rituals, but the following are just the common ones; mugwort, wild thyme, verbena, chamomile, lemon, hemp, oak, and lavender.

Trees

The oak tree has always been significant during Litha because of the Oak King and Holly King.