The climate of Kamloops is semi-arid (Köppen climate classification BSk) due to its rain shadow location. Because of milder winters and aridity, the area west of Kamloops in the lower Thompson River valley falls within Köppen climate classification BWk climate. Kamloops gets short cold snaps where temperatures can drop to around −30 °C (−22 °F) when Arctic air manages to cross the Rockies and Columbia Mountains into the Interior; this does not happen every winter but less often can lock in for weeks.
The January mean temperature is −4.2 °C (24 °F). That average sharply increases to 4 °C (39 °F) by February. The average number of cold days below−10 °C (14 °F) per year is 8 as recorded by Environment Canada.
Although Kamloops is located above 50° north latitude, summers are warm to hot with prevailing dry, and sunny weather. Daytime humidity is generally very low (less than 20%) which allows for substantial nighttimes cooling. Occasional summer thunderstorms can create dry-lightning conditions, sometimes igniting forest fires which the area is prone to.
Spring and Fall are usually pleasant and dry but can be short in duration.
The city has spring and summer water restrictions: in effect only from May 1 to August 31.
Kamloops lies in the rain shadow leeward of the Coast Mountains and is biogeographically connected to similar semi-desert areas in the Okanagan region, and a much larger area covering the central/eastern portions of Washington, Oregon and intermundane areas of Nevada, Utah and Idaho in the US.
These areas of relatively similar climate have many distinctive native plants and animals in common, such as Ponderosa Pine (Pinups ponderosa), big sagebrush (Artemisia tridentate), prickly pear cactus (Pontiac fragile in this case), rattlesnakes (Cortiles virilise), Black widow spiders and Lewis's Woodpecker
