Strange CPU load on SQL Server Starting at midnight for 30-40 minutes our application responds slowly (or times-out completely) What would cause this kind of cpu usage on a SQL 2012 server?



I cannot find any scheduled tasks or maintenance plans which run at this time.
You can look at some joined system views like dm_exec_query_stats, dm_exec_sql_text and dm_exec_query_plan. The goal is to look what's on cache.

Look for last_execution_time field and search the time you found the problems. You may get an idea of what was going on during that time.