Clouds and sleet, rain and even snow may prevent Washington from seeing the sun Tuesday at one of the pivotal moments of the astronomical year.

At 12:15, p.m. eastern daylight time, the sun will be. (or more properly, SEEM to be) poised in a position of equality of illumination between the northern and southern hemispheres.

As it does for only two momentous instants each year, it will appear to be directly above the equator, favoring with its life-giving warmth neither the areas of our planet above the equator or those below.

But according to the latest forecasts, almost every kind of wintry precipitation in the arsenal of cold weather may prevent us from glancing at the solar orb , as an act of celebration of the moment, and possibly awe at the regularity of Earth’s orbital motion..

Which may be just as well, of course, unless we have held onto our eclipse glasses from last summer. Looking with the unprotected eye upon the solar disk is a prescription for incurring damage to the eye.

But this should not prevent a recognition of the moment. Afterward, the sun will seem to cross the equator, and favor us in the northern hemisphere for six months. Then it will cross again in September, at the time of the second equinox of the year.

So it may snow. Sleet may fall. And cold rain. But that sun, according to all the laws of physics and astronomy, can not be stopped. If anything can be said with certainty, it is that it will continue on its annual pilgrimage until it stands (or seems to stand) above the tropic of cancer.

That will be the moment of the summer solstice. It will come in June. But let us not get ahead of the game. Tuesday is the equinox, the vernal equinox. Whether we see the sun or not, whether we wear galoshes and hooded coats or not. The time will be 12:15 p.m.