In the northern hemisphere the sun has come back for the season. Edgar Cayce frequently impressed the importance of light to people's health.
On a search this morning I found the following readings:
Take as much outdoor exercise as is possible in sunshine. Should the sunshine seem to produce headaches and strain on eyes, these conditions will be found to be remedied by wearing dark glasses or shading the eyes. The vitality as caused from the sun will be effective toward vitalization of the body. [81-2 F ADULT - 30th day of January, 1928]
3. In the building up, then - be mindful of the diet, be mindful that the conditions in throat and bronchia are not IRRITATED TOO much by either the night air or dust, or such irritants, or by too much SMOKING [...]. Keep the eliminations well in the alimentary canal. Keep those of the body exercise, especially of mornings. Follow the morning exercise with a good brisk RUB, and let a portion of the rub be with cold water along the spine. Keep the manipulations
occasionally, and the sun as often as possible - with not too great a period of such sunning during this period of the year. Ready for questions. [137-132 M 31 - 4th day of July, 1930]
In a reading in January, Cayce said to get as much sunshine as possible. In a reading in July, Cayce said sun is important, but not too much "during this period of the year".
I thought this reading, for a 16 year old woman, was cute:
(Q) What is the best formula that will make my skin brown from the sun?
(A) Sun tan for some is good. But for those that have a certain amount of pigment in the skin, as indicated in this body, to make for variations as to the effect of weather or sun upon exposed portions of the body - made up of the atomic vibrations to which the circulation in various portions of the body is reactive - to get a sun tan would not be well for this body; for it would burn tissue before it would tan. That which would be more effective (if the body is insistent that
it desires the tan) would be the use of vinegar and olive oil (not vinegar made from acetic acid, or synthetic vinegar, but the use of that made from the apples) combined with coffee made from resteaming or re-vaporing used coffee grounds. The tannin in each of these, and the acids combined, would become very effective. But it will wear off, of course, in a very short time even - if used. [276-7 F 16 (Student, Protestant)]
Modern scientists have discovered a lot about light. This blog post from an illumination engineering society, informs of how exposure to sunlight in the early morning inoculates against sunburn at midday:
Excess amounts of ultraviolet radiation can cause erythema (sunburn) in the short term, and photoaging and skin cancers in the long term. Curiously, pre-exposure to IR-A radiation preconditions the skin, making it less susceptible to UV-B radiation damage (Menezes et al. 1998). This is probably an evolutionary adaptation, as the atmosphere absorbs and scatters ultraviolet and blue light in the morning hours shortly after sunrise (Barolet et al. 2016). This morning
exposure to IR-A radiation is likely taken as a cue to ready the skin for the coming mid-day exposure to more intense ultraviolet and near-infrared radiation. Late afternoon exposure to decreased amounts of ultraviolet radiation may further be taken as a cue to initiate cellular repair of the UV-damaged skin. In this sense then, solar near-infrared radiation is an identified benefit.
Modern weather apps have a field for UV Index: https://www.epa.gov/sunsafety
This reading, from 0 (no danger) to 11 (sunburn quickly) gives the intensity of ultraviolet radiation at a given location.
Some of Cayce's other readings impressed the importance of avoiding the sun from 10am to 2pm, when the sunburn-inducing ultraviolet light is strongest.
Bright light is the a good inoculant against infections. If you live in the southern hemisphere, having a bulb than emits plenty of red light (heat lamp, halogen bulbs, Warm-white LED, etc) is a decent substitute for the summer sun.
You can also ground yourself by using a metal fork on the tops & bottoms of your feet, by walking barefoot in grass, or by taking a bath with epsom salts and/or baking soda.