Having tracked down Aster, I am not sure he is referring to the effects of rain. It appears to me that Vandamme doubled teams to cope with the poor quality of the roads.
Aster, Heinrich, Die Kriegsereignisse zwischen Peterswalde, Pirna, Königstein und Preisten im August 1813 und die Schlacht bei Kulm, Dresden 1845
From page 65, a rough translation:
'According to the diary of the fortress Königstein, General Vandamme had the fortress commandant informed on August 26th at 2:00 am that he wanted to attack the enemy at dawn and throw them out of the vicinity of the fortress. He caused the fortress commander to support him wherever possible with gunfire from the fort, and even to fire on individual Cossack troops of 10 to 12 men.
At dawn the four battalions of the Creuzer Brigade left the camp on the Lilienfteine, passed the ship's brothers and, under Vandamme's orders, entered the right bank of the Elbe. Two of these battalions went through the town of Königstein around the fortress to the left and marched in a closed column on the height behind the paper mill to Kriezschwitz. The two other battalions used the road to the fortress and took a position at the new tavern. Tirailleurs of both divisions immediately advanced into the forest at the foot of the fortress. The battle with the Russian outposts located there began after 6 o'clock in the morning and they were pushed back on their right wing against Kriezschwitz and on their left wing against the village of Struppen. The rest of the men of these battalions, however, remained standing on both wings in column and, since there was no artillery available, but the Russians had brought up four pieces, which caused much damage to the former, could only advance to the edge of the forest.
As the tirailleurs advanced, the enemy outpost standing in front of the troops was fired at from Königstein fortress from two 24-pound cannons, whereupon he retreated.
The fortress commander had to give General Vandamme at quarter of an hour intervals news of everything that was discovered from the fortress in relation to the enemy. The skirmish continued through the morning, but no part made progress; for after the Russians were thrown out of the forest, they found themselves in the open field without any cover. The French, on the other hand, were deprived of the artillery, which was still far behind, and since they were held in check by the enemy guns, they could not leave the wood or advance further. Around noon in the town of Königstein, around 300 to 400 French people had returned.
During this battle the Corps of General Vandamme, which had cantonned in the vicinity of Rumburg, Neustadt near Stolpen and Bauben until August 24th and 25th, approached the Elbe on the 26th from Neustadt and Stolpen.
The divisions Dumonceau and Philippon came from Neustadt via Ehrenberg to Hohnstein and the brigades Dufour, Reuss and Quiot via Lang-Wolm S. Dorf, Heeselicht and Hof-Burkersdorf. The first troops from the Dumonceau division were the Anhalt-Defrau Dragoon Regiment, which arrived at around 9 o'clock.
In the morning the town of Hohnstein popped up. This was followed by the other regiments in a tightly packed mass, whose march continued until late in the evening. The artillery assigned to these troops was held up on the march immensely in these steep mountains, especially on the Wartenberg, opposite Hohnstein. In order to bring the guns to Lestern, their teams had to be doubled, whereby the undoubled wagons remained standing on the Polenzbach until they were caught up in the same way by the double-carts brought back again. The night of August 26th to 27th fell over it and a large number of troops moved into their bivouaks in Polenzthale. The watch-fires blazed up high after Mockstone; Fortunately, there was no fire in the small town on the steep hillside,
The other wagons, which could not be brought further because of the stalls in the valley and the guyed wagons, stood one behind the other through the whole town as far as the so-called Vorwerk.
Many of the leader farmers used this nightly stay to harness their horses and ride away, so that the next morning (on August 27th) a large number of horses had to stand still until new leader horses were created.
The delay and slowness of the march of the French artillery when crossing the Wartenberg, the Ziegenrůck and the long mountain slopes on the Lilienftein flatness and on the Königsteiner Berge can easily be explained from the foregoing.'