Early-season Thermals

Early in the season (or early in the day), convection is comparatively weak and inconsistent.   Individual thermals are typically small and not apt to rise very high, because they are also short-lived.   Only zero-sink may be available at first, but the quality of lift can be expected to improve.   Early lift that dies may re-form almost immediately, so after a short climb tops out it might pay to return to the same source and try again.   When another thermal rises, it may be stronger – or it could be weaker, and the next one stronger…
Late in the day (or season), expect each successive thermal to be weaker than the one before, and plan accordingly.   Evening (or autumn) thermals are softer, too.   This can make them more difficult to detect, yet easier to work.   The good ones will be wider than their morning (or spring) counterparts, and may rise, however slowly, almost as high as those of the convective maximum hours earlier.