Spring is the best time to visit — March through early May brings wildflower season, with bluebonnets and Indian paintbrush covering the roadsides and pastures across the Hill Country. Temperatures are mild and the landscape is at its most photogenic. The Kerrville Folk Festival runs for eighteen days in late May and early June, drawing large crowds to Quiet Valley Ranch; if you are coming for it, book accommodation well in advance.
Summer is hot — highs regularly above 95°F (35°C) — but the Guadalupe River makes it bearable, and the tubing and swimming crowds embrace the heat as part of the experience. River water stays cooler than air temperature, fed by springs. Fall is pleasant and less crowded, with temperatures dropping to comfortable levels by October. Winter is mild by northern standards (freezing temperatures are occasional but not sustained) and very quiet; most outdoor attractions remain open, and the Hill Country without summer crowds has a different and unhurried character.
Cedar fever — an allergic reaction to mountain cedar pollen — hits hard in December and January. If you are susceptible to tree pollen allergies, avoid this window.