We present a study of the streamer-to-spark transition in a self-pulsing dc-driven discharge called a transient spark (TS). The TS is a streamer-to-spark transition discharge with short spark duration (∼10-100 ns), based on charging and discharging of the internal capacity of the electric circuit with repetition frequency 1-10 kHz. The TS can be maintained under relatively low energy conditions (0.1-1 mJ pulse −1). It generates a very reactive non-equilibrium air plasma applicable for flue gas cleaning or bio-decontamination. Thanks to the short spark current pulse duration, the steady-state gas temperature, measured at the beginning of the streamers initiating the TS, increases from an initial value of ∼300 K only up to ∼550 K at 10 kHz. The streamer-to-spark transition is governed by the subsequent increase in the gas temperature in the plasma channel up to ∼1000 K. This breakdown temperature does not change with increasing repetition frequency f. The heating after the streamer accelerates with increasing f , leading to a decrease in the average streamer-to-spark transition time from a few µs to less than 100 ns.