as it is expected, july 1941 was rainy and october 1941 was colder than usual. The following text is from https://www.britannica.com/event/World-War-II/Invasion-of-the-Soviet-Union-1941
On June 22, 1941, the German offensive was launched by three army groups under the same commanders as in the invasion of France in 1940: on the left (north), an army group under Leeb struck from East Prussia into the Baltic states toward Leningrad; on the right (south), another army group, under Rundstedt, with an armoured group under Kleist, advanced from southern Poland into the Ukraine against Kiev, whence it was to wheel southeastward to the coasts of the Black Sea and the Sea of Azov; and in the centre, north of the Pripet Marshes, the main blow was delivered by Bock’s army group, with one armoured group under Guderian and another under Hoth, thrusting northeastward at Smolensk and Moscow.
The invasion along a 1,800-mile front took the Soviet leadership completely by surprise and caught the Red Army in an unprepared and partially demobilized state. Piercing the northern border, Guderian’s tanks raced 50 miles beyond the frontier on the first day of the invasion and were at Minsk, 200 miles beyond it, on June 27. At Minsk they converged with Hoth’s tanks, which had pierced the opposite flank, but Bock’s infantry could not follow up quickly enough to complete the encirclement of the Soviet troops in the area; though 300,000 prisoners were taken in the salient, a large part of the Soviet forces was able to escape to the east. The Soviet armies were clumsily handled and frittered their tank strength away in piecemeal action like that of the French in 1940. But the isolated Soviet troops fought with a stubbornness that the French had not shown, and their resistance imposed a brake by continuing to block road centres long after the German tide had swept past them. The result was similar when Guderian’s tanks, having crossed the Dnieper River on July 10, entered Smolensk six days later and converged with Hoth’s thrust through Vitebsk: 200,000 Soviet prisoners were taken; but some Soviet forces were withdrawn from the trap to the line of the Desna, and a large pocket of resistance lay behind the German armour. By mid-July, moreover, a series of rainstorms were turning the sandy Russian roads into clogging mud, over which the wheeled vehicles of the German transport behind the tanks could make only very slow progress.