The Noda Beyehudah rules that one is allowed to interrupt the reading of the megillah on Purim in order to recite kiddush levanah. It would seem that the same should apply if there is thunder and lightning whilst reading the megillah. However here there could be some additional points.  Since one must recite the berachah for these things “toch kedai dibur”, which is about three seconds, one might well have to say these berachot even in the middle of a verse of the megillah. In such a case would one return to the next word or the beginning of that verse? Another point is that because light travels much faster than sound, there could well be a space of over half a minute between seeing the lightning and hearing the thunder. Would one wait in silence after saying the berachah over the lighting until one hears the thunder, or alternatively would one meanwhile read another verse or so of the megillah? A related issue is if during the reading the megillah, someone calls out that there is a rainbow outside, would one then interrupt the reading and go outside to recite the berachah, as in the case of kiddush levanah?