Because “space weather,” caused by events on the sun, impacts radio propagation, some people like to check the propagation forecast before heading out on a SOTA activation. There are a number of sites which put together a forecast. I’ve embedded some of them at my Radio Happiness Forecast page.
This page is ironically named. So far, I’ve found little value in the propagation forecast. I’ve had bad days when the forecast was good and vice versa. Despite the fact they are caled “forecasts,” they really report on how propagation should be right now. The values change between the time I leave the house at 6 A.M. and when I activate the summit at 1 P.M. (for example).
There are other important variables when you’re transmitting atop a mountain which can outweigh the propagation forecast. For example, I’ve found that a sharply defined apex seems to really boost signal strength (with the antennas I use), and a broad, flat summit seems to attenuate.
Clearly, you won’t make transoceanic contact if the propagation isn’t there, but… If the forecast is poor, don’t let that stop you from heading out the door. If the forecast is great, but you really didn’t want to activate today, don’t go just because the forecast is good. I’ve had great results at 11 A.M. when the forecast was poor at 6 A.M. Note that I’ve not yet attempted an activation when the forecast was for heavy blackouts due to a major CME.
Check the weather forecast, and cancel your trip if it is going to rain on your activation, but don’t let a bad solar weather forecast cancel your trip.