1. In accordance with the season
   "it was seasonably cold" 
2. At an opportune time
   - timely, well-timed, apropos

See also: seasonable

Antonym: unseasonably

• downdraught
• downer
• downfall
• downfallen
• downfield
• downgrade
• downhearted
• downheartedness
• downhill
• downiness
• Downing
• Downing Street
• downlike
• downline
• download
• downloadable
• downmarket
• downpipe
• downplay
• limited war
• limitedly
• limiter
• limiting
• limitless
• limitlessness